Background and study aim: The aim of this study was to assess the prevalence of nonpolypoid lesions (NPLs) in Italy and their risk of containing neoplasia or advanced histology. Patients and methods: This was a multicenter cross-sectional observational study on consecutive patients undergoing total colonoscopy over a 3-month period in 80 Italian centers. Results: In all, 27 400 total colonoscopies were analyzed. Cancer was diagnosed in 801 patients (2.9 %). A total of 6553 precancerous lesions were detected in 5609 patients. Of these, 4154 patients (74.1 %) had polypoid lesions and 1455 patients (25.9 %) had NPLs. Therefore, the prevalence of NPLs was 5.3 % (95 %CI 5.0 – 5.6). NPLs larger than 10 mm were detected in 254 patients (17.5 %). NPLs were more predominant in the proximal colon (OR 2.92, 95 %CI 2.56 – 3.43; P < 0.0001 vs. polypoid lesions). Neoplastic tissue was diagnosed in 79.0 % and advanced histology (high-grade intraepithelial neoplasia or more) in 20.9 % of resected lesions. The risk of advanced histology was similar for polypoid and nonpolypoid lesions when adjusted for size. Depressed lesions had the highest risk of advanced histology (OR 10.56, 95 %CI 6.02 – 18.55; P < 0.0000 vs. flat-elevated). Age was an independent predictor of both neoplasia and advanced histology (P = 0.0001). Conclusions: NPLs are relatively common in the Italian population, with a prevalence similar to that in other Western series. NPLs are not more aggressive than polypoid lesions, except for those with depressed morphology.