Objective An association between diverticulosis and colorectal neoplasms may have implications for colonoscopic prevention of colorectal cancer. We aimed to examine the association between diverticulosis and colorectal polyps with special attention to the age at diagnosis, the anatomical location, and the histological subtype of colorectal polyps. Methods We included all consecutive patients referred for routine colonoscopy between February 2008 and February 2009. We recorded the presence of diverticulosis (defined as at least two diverticula) and colorectal polyps (adenomas and serrated polyps). Results We included 2310 patients (46.1% men, mean age 58.4 years), of which 37.0% had diverticulosis and 34.2% had one or more colorectal polyps. Multiple logistic regression analysis, including age, sex, and interaction terms with diverticulosis, showed that the association between diverticulosis and colorectal polyps was significantly influenced by age (P = 0.009). In patients aged below 60 years, prevalence of colorectal polyps was significantly higher in those with diverticulosis compared with those without diverticulosis: 39.1% (79 of 202 patients) versus 19.6% (176 of 898 patients), adjusted odds ratio (OR) 1.87, 95% confidence interval (CI) 1.26-2.78, and P = 0.002. This association was found for both proximal and distal polyps and for all histological subtypes, namely adenomas (adjusted OR 1.60, 95% CI 1.02-2.49, P = 0.04), serrated polyps (adjusted OR 1.73, 95% CI 1.03-2.91, and P = 0.04), and advanced neoplasms (adjusted OR 2.32, 95%CI 1.31-4.12, P = 0.004). Conclusion Presence of diverticulosis in patients aged below 60 years may be considered a 'red flag' for synchronous adenomas, serrated polyps, and advanced neoplasms. Diverticulosis may represent an indication for earlier initiation of colorectal cancer prevention programs. Eur J Gastroenterol Hepatol 23:1050-1055 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.