--- title: "L.E.K. Case Interview 2026: How CDD Engagements Become the Case Format" description: "Updated May 11, 2026 | By Florian Smeritschnig, Former McKinsey Senior Consultant L.E.K. case interviews are unusual among major consulting firms in this specific way: they're not abstract business..." url: https://strategycase.com/lek-case-interview/ date: 2026-05-12 modified: 2026-05-12 author: "Florian Smeritschnig" image: https://strategycase.com/wp-content/uploads/2026/05/L.E.K.-Case-Interview.png categories: ["L.E.K. Consulting", "Case Interview"] type: post lang: en --- # L.E.K. Case Interview 2026: How CDD Engagements Become the Case Format *Updated May 11, 2026 | By (https://strategycase.com/about/), Former McKinsey Senior Consultant* (https://www.lek.com/) case interviews are unusual among major consulting firms in this specific way: they’re not abstract business problems designed to test consulting skills in the abstract. They’re compressed simulations of the actual work L.E.K. does on commercial due diligence engagements. The format, the math patterns, the analytical sequence, even the written case packet — all map directly to a 2-4 week CDD project. Once you see the mapping, the entire interview becomes more predictable, and prep gets sharper. This guide walks through the CDD-to-case mapping, breaks down L.E.K.’s case format across both rounds and the written case, covers the “layered math” pattern the firm is known for, and gives three sample case prompts drawn from CDD-style scenarios in healthcare, consumer, and industrial sectors. ## **Key Takeaways** - L.E.K. cases mirror the analytical sequence of a commercial due diligence engagement: market sizing → growth assessment → competitive position → customer validation → financial model → recommendation. - First round: two 30-40 minute interviews combining short behavioral content with candidate-led cases. Final round (Superday): 2-3 senior consultant or manager interviews with longer, more intense cases that may include multiple segments. - L.E.K. is known for “layered math” — multi-step calculations chaining market growth × penetration × pricing × EBITDA impact. Math precision under time pressure matters more than at most peer firms. - The 60-minute written case (40-50 page dense packet → 8-10 slide deck) is the differentiator and the most under-prepared component. - Healthcare and life sciences cases are very common across all rounds, even for candidates not applying to the healthcare practice. ## **The CDD-to-Case Mapping** Most prep guides teach L.E.K. cases as “candidate-led growth strategy or market entry cases with heavy math.” That’s accurate but misses why the cases are designed the way they are. Once you understand that L.E.K. cases compress a real CDD engagement into 40 minutes, the analytical sequence falls into place. ### **What L.E.K. actually does in a CDD engagement** A typical 3-week CDD engagement runs through six analytical layers, roughly in this order: 1. Market landscape — How big is the market? What’s the growth trajectory? What’s the segmentation? 2. Growth assessment — What drives growth in this market? Is the target’s growth thesis credible? 3. Competitive position — Who competes? What’s the target’s position? Is it defensible? 4. Customer perspective — What do customers actually need and want? Is the target meeting it? 5. Financial model — What does the math actually look like? Revenue, EBITDA, working capital, capex? 6. Investment recommendation — Should the PE firm invest? What’s the value creation path? ### **How those six layers show up in case interviews** L.E.K. cases rarely require you to do all six in a single 30-40 minute case. But most cases require three to four of them, and the way the interviewer probes signals which layers they’re testing. **(https://strategycase.com/market-sizing-case-interviews/) prompt** → tests layer 1 plus light layer 5 math **(https://strategycase.com/growth-strategy-case-interview/) prompt** → tests layers 2 and 3 plus financial implications **(https://strategycase.com/market-entry-case-interview/) prompt** → tests layers 1, 3, and the competitive entry math **(https://strategycase.com/profitability-case-interview/) prompt** → tests layer 5 with diagnostic layer 4 elements **(https://strategycase.com/mergers-and-acquisitions-case-interview/) prompt** → tests all six in compressed form (these appear most often in final rounds) The pattern recognition matters: candidates who recognize which CDD layers a case is testing structure their analysis around those layers rather than reaching for generic frameworks. ## **The Case Interview Format Across Rounds** L.E.K. runs a two-round case interview process with distinct shapes at each round. ### **First round: Two 30-40 minute interviews** Conducted by Consultants or Managers (rarely by junior consultants — the firm prefers experienced interviewers even at first round). Each interview includes: - 5-10 minutes of behavioral questions covering motivation, fit, and brief experience walk-through - 25-30 minutes of candidate-led case The first-round case format is typically a single business problem with frequent interviewer probing. The interviewer pushes back on weak analyses, asks for justification on framework choices, and tests depth at each step rather than just letting you run through. **Common first-round case types:** - Profitability case (testing diagnostic ability) - Market entry case (testing CDD-style market analysis) - Growth strategy case (testing commercial thinking) ### **Final round (Superday): Two to three interviews** Held at the office. Conducted by Managers, Principals, and sometimes Partners. Each interview runs 45-60 minutes and includes: - Brief behavioral content - Live case interview (often more complex than first round) - Sometimes a multi-segment case combining profitability + market sizing + recommendation **The written case** is added at the final round in most offices. We cover it separately below. ### **Why L.E.K. interviewers probe more than peers** L.E.K. interviewers are widely reported as more aggressive in probing case analyses than McKinsey or BCG interviewers. The reason connects to the firm’s work: in a CDD engagement, the partner’s job is to challenge every claim before the recommendation reaches the PE client. That habit carries into case interviews. Candidates who can defend their reasoning under sustained probing pass. Candidates who fold or hedge fail, even if their initial structure was reasonable. For broader case interview fundamentals, see our (https://strategycase.com/consulting-case-interviews-a-comprehensive-guide/). ## **The “Layered Math” L.E.K. Cases Are Known For** The math bar at L.E.K. is higher than at most tier-2 firms, comparable to Oliver Wyman, and shaped specifically by the CDD analytical sequence. The signature pattern is “layered math”: a multi-step calculation chaining several variables to reach a financial implication. ### **A typical layered math chain** A complete CDD financial model includes calculations along these lines: 1. Market size = customers × spend per customer 2. Addressable market = market size × addressable share 3. Revenue opportunity = addressable market × company’s expected penetration × pricing 4. Gross profit = revenue × gross margin 5. EBITDA contribution = gross profit − allocable operating expenses 6. EBITDA impact on enterprise value = EBITDA × applicable multiple 7. NPV adjustments for timing and risk In a case interview, you won’t run this full chain. But you’ll often run 3-5 sequential steps, with each step compounding precision requirements. Errors at step 2 cascade to wrong answers at step 6. The firm tests whether you can hold the chain in your head, execute each step cleanly, and reconcile back to a coherent answer. ### **What this requires for prep** **Mental math fluency across percentage and ratio operations.** Standard prep is necessary but not sufficient. **Sequential calculation discipline.** Practice running 4-6 step calculation chains under time pressure without losing track of which number connects to which. **Reconciliation habits.** When you finish a multi-step chain, check whether the answer makes intuitive sense before committing to it. Sanity-check against alternative paths. For practice on this specific math pattern, see our (https://strategycase.com/case-interview-math/), which include layered calculations. ## **Three Sample Case Prompts (CDD-Style)** Below are three case prompts modeled on actual L.E.K. case patterns. Note the deal-evaluation framing on two of three. ### **Sample Case 1: Healthcare Services CDD** > Our client is a mid-market private equity firm considering a $400 million acquisition of a US-based ambulatory surgery center (ASC) network with 24 locations across the Southeast. The PE thesis is that ASC volume will grow at 6-8% annually as procedures continue migrating from hospital outpatient departments. The PE firm has asked us to validate the growth thesis and the company’s competitive position. They need our findings in 3 weeks. How would you approach this? **What this tests:** - Healthcare services literacy (you should know that the ASC market is real and what’s driving it) - CDD analytical sequence — market sizing, growth validation, competitive position, financial implications - Comfort with the deal-timeline constraint (you can’t run a 6-month analysis; what’s the 3-week priority sequence?) - Layered math: TAM × addressable share × company penetration × revenue per case × margin **Common candidate failure modes:** - Defaulting to a generic market entry framework instead of CDD analytical sequence - Missing the regulatory and reimbursement dimensions of US healthcare services - Failing to address the 3-week timeline as a structural constraint on the analysis - Math errors in the multi-step revenue and EBITDA chain ### **Sample Case 2: Consumer Brand Growth Strategy** > Our client is a $300 million revenue direct-to-consumer (DTC) skincare brand with strong online performance but limited retail distribution. The CEO wants to know whether to expand into traditional retail channels (Sephora, Ulta, Target) and, if so, how. We’ve been engaged for a 4-week strategic review. Walk me through your approach. **What this tests:** - Consumer/retail strategy thinking (channel economics, brand positioning, distribution trade-offs) - Quantitative analysis of channel economics (DTC vs wholesale margin structures) - Customer-perspective layer — what’s the consumer overlap between channels? - Competitive position analysis — what do similar brands do at this revenue scale? **Common candidate failure modes:** - Generic 4Ps framework without consumer-specific consideration - Missing the channel economics: DTC gross margin runs 70-80% while wholesale runs 40-50% - Failing to address brand cannibalization risk between channels - Recommending “go retail” or “stay DTC” without quantifying the financial trade-off ### **Sample Case 3: Industrial Equipment Acquisition** > Our client is a mid-market PE firm considering a $700 million acquisition of a US-based manufacturer of specialty industrial valves. The target has $250 million in revenue, 18% EBITDA margins, and serves oil & gas, chemical processing, and water treatment end markets. The PE firm sees a thesis around international expansion. They need a 3-week CDD with focus on the international growth thesis. What’s your approach? **What this tests:** - Industrial sector literacy (you should know the basics of valve manufacturing and end-market dynamics) - International expansion analysis (which markets, what mode, what capital) - Competitive position assessment in fragmented industrial markets - Financial modeling: revenue ramp, capex requirements, EBITDA contribution **Common candidate failure modes:** - Treating industrial valves as interchangeable with generic industrial products - Missing the end-market diversification angle (oil & gas vs chemical vs water — different cyclicalities) - Recommending international expansion without engaging with the capital requirements and timeline - Failing to translate the CDD findings into an investment recommendation ## **The 60-Minute Written Case** The written case is the most under-prepared component of the L.E.K. final round. Format: - **Time:** 60 minutes total - **Materials:** A dense packet of 40-50 pages including business scenario, market data, financials, customer data, and specific questions - **Output:** A 8-10 slide PowerPoint presentation (or paper-based equivalent in some offices) - **Presentation:** 15-20 minutes presenting and Q&A with senior consultants This format compresses a real CDD presentation into 60 minutes of prep plus 15-20 minutes of delivery. It’s structurally more demanding than (https://strategycase.com/oliver-wyman-case-interview/) (30 min prep + 30 min present) because of the dense packet and slide expectation. For more on this topic, see our (https://strategycase.com/how-to-crack-written-case-interviews/). ### **What wins the L.E.K. written case** - **Read the questions first, then scan the packet for relevance.** You can’t read 40-50 pages in 10 minutes. Identify the questions, then extract the data you need. - **Title-as-conclusion slides.** Every slide title states a conclusion (“Healthcare services growth thesis supported by 7% TAM CAGR and aligned demographics”), not a topic. - **Reconciled numbers.** Every financial number ties to source data. CDD work depends on numerical reconciliation; the firm tests this in the case. - **8-10 slides, not more.** The output is a tight diligence deck, not a comprehensive analysis. Discipline matters. - **Implicit recommendation structure.** Lead with the answer (invest / don’t invest, expand / don’t expand). Detail follows. - **Risk slide.** What could break the thesis. The firm wants this; don’t skip. ### **What loses the L.E.K. written case** - **Sequential walkthrough of the packet.** The packet is input. Your output is synthesis. - **No clear recommendation.** Hedged conclusions fail. - **Slides full of bullets without thesis titles.** The CDD work product discipline matters. - **Math that doesn’t reconcile.** Caught immediately by experienced reviewers. - **Time mismanagement.** Most candidates underestimate how dense 40-50 pages is. ## **How to Prep for the L.E.K. Case** L.E.K. case prep diverges from general consulting prep in three specific ways. Build prep capability in this sequence. ### **Layer 1: CDD analytical fluency (3-4 weeks)** Build genuine understanding of the CDD analytical sequence — market, growth, competition, customer, financial, recommendation. Useful resources: - L.E.K.’s own published case studies on their website (read 5-10 across healthcare, consumer, industrials) - PE-focused publications (Bain Global PE Report annually, McKinsey PE practice publications) - Industry-specific reading in your target practice (healthcare services, biopharma, consumer DTC, industrials) Goal: when you read a case prompt, you can immediately identify which CDD layers are being tested. ### **Layer 2: Layered math drilling (2-3 weeks intensive)** Build mental math fluency on multi-step calculation chains. Practice: - 4-6 step calculation sequences without losing track - Quick reconciliation between calculation paths - Mental conversion between percentages, ratios, and absolute numbers The (https://strategycase.com/case-interview-math/) covers L.E.K.-style patterns specifically. ### **Layer 3: Case practice with CDD framing (3-4 weeks)** Run 15-20 individual cases with a mix: - 6-8 CDD-style cases (healthcare, consumer, industrial — pick the sector matching your target practice) - 4-5 profitability and market entry cases - 3-4 growth strategy cases - 2-3 multi-segment cases (typical of final rounds) Practice driving the case from CDD analytical sequence, not generic frameworks. ### **Layer 4: Written case simulation (1-2 weeks)** Most-under-prepared. Find 2-3 dense business cases (HBS cases work well, particularly PE diligence cases) and simulate: - 60-minute reading and analysis - 8-10 slide deck on paper or in PowerPoint - 15-20 minute presentation to a partner who plays the interviewer - Iterate on weak presentation skills For one-on-one preparation tailored specifically to the L.E.K. format, (https://strategycase.com/florian-coaching/) is available. ## **Frequently Asked Questions** ### **How is the L.E.K. case interview different from BCG or Bain?** L.E.K. cases mirror commercial due diligence analytical sequences more directly than BCG or Bain cases. The math is more layered (multi-step calculation chains testing precision under time pressure). Interviewers probe more aggressively. Healthcare and PE-flavored cases appear more frequently. The 60-minute written case format with 40-50 page packets is more demanding than BCG or Bain equivalents. ### **What case types does L.E.K. use most often?** Market sizing, growth strategy, market entry, and profitability cases dominate. Healthcare cases are common across all rounds — even non-healthcare applicants should expect to face at least one. PE-flavored cases (acquisition evaluation, growth thesis validation) appear most often in final rounds. ### **How hard is the L.E.K. written case?** Among the most demanding written cases in major firm consulting. 60 minutes to read a 40-50 page dense packet and produce an 8-10 slide presentation, then 15-20 minutes presenting. The density of the packet plus the slide-quality expectation makes it more demanding than (https://strategycase.com/oliver-wyman-case-interview/). ### **Do you need healthcare background to pass L.E.K. cases?** Helpful but not required. Healthcare cases appear across all rounds even for non-healthcare applicants, so building baseline healthcare services and biopharma literacy is useful for all candidates. Candidates with explicit healthcare background (MD, PhD, biotech, pharma) have a meaningful fit advantage if targeting the healthcare practice. ### **Can I use a calculator in the L.E.K. case interview?** Not in the live case interview — mental math is required throughout. The written case is paper-based at most offices and doesn’t include a calculator. Some offices may allow a basic calculator in the written case; confirm with your recruiter. The (https://strategycase.com/lek-numerical-reasoning-test/) (early screening assessment) is also no-calculator. ### **What’s the most common mistake on L.E.K. cases?** Defaulting to generic strategy frameworks (4Ps, Porter’s five forces, 3Cs) instead of structuring around the CDD analytical sequence. L.E.K. interviewers can recognize generic frameworks immediately and probe harder when they see them. Candidates who structure around market-growth-competition-customer-financial-recommendation show they understand the firm’s actual work.