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Objective Colonoscopic surveillance is crucial for early diagnosis and prevention of colorectal cancer (CRC) in Lynch syndrome (LS). Since July 2023 in England, colonoscopic surveillance has been incorporated as a national screening programme; however, historical data to inform gene-specific neoplasia detection rates predominantly derive from cohorts with poorly reported quality standards. We aimed to identify risk factors for colorectal neoplasia in a LS cohort with high baseline colonoscopic quality standards.Methods A retrospective evaluation of patients with LS was conducted at a tertiary centre (January 2019–January 2025). Demographics and clinicopathological data, including colonoscopy quality factors, were extracted. Factors influencing adenoma (ADR), advanced adenoma (AADR), serrated lesions (SSLDR) and CRC detection rates (CRCDR) were evaluated.Results Among 473 patients undergoing 992 colonoscopies, 98% achieved caecal intubation and 96% had adequate bowel preparation over a median follow-up of 30 months. The ADR, AADR, SSLDR and CRCDR were 31.3%, 6.8%, 13.5% and 2.8%, respectively. Adenomas were predominantly proximal (68.4%), non-advanced (87.7%) and flat (38.6%). Age, body mass index ≥25 kg/m 2 and hyoscine butylbromide increased ADR, while male gender and non-white ethnicity increased CRCDR. MLH1 had the lowest ADR (24.5%), however accounted for 50% of CRCs. Higher SSLDRs were identified in MSH6/PMS2 (vs MLH1/MSH2) carriers, however no significant differences were found in ADR, AADR and CRCDR between high-risk and low-risk genotypes.Conclusion We demonstrate a high adenoma burden with distinct phenotypic and gene-specific characteristics in a UK LS population undergoing high quality surveillance. This supports the need for high baseline quality standards and optimising genotype-tailored surveillance protocols.