Adenomas in Lynch syndrome have an accelerated progression to colorectal cancer (CRC) which might occur despite a regular follow-up. Despite low evidence, high-definition technology (HD) and indigo-carmine chromoendoscopy (CE) are recommended for surveillance in Lynch syndrome.The investigators will conduct a prospective multicenter randomized non-inferiority study. The principal aim is to compare the adenoma detection rate with WLE vs CE. Our hypothesis is that HD-white-light endoscopy (WLE) is not inferior to CE. Therefore - under expert hands - HD-CE does not add any significant advantage over HD-WLE on adenoma detection rate in patients with Lynch syndrome.