Tandem colonoscopies studies results, show that novel endoscopic technologies detect about 20% more adenomas than those conventional colonoscopy does (missed adenomas). Since Endocuff-assisted colonoscopy cannot be considered as a perfect examination, we hypothesize that conventional colonoscopy will detect one third of the missed adenomas that Endocuff-assisted colonoscopy detects in a similar setting. Therefore a sample size of 120 adenomas achieves 80% power to detect an odds ratio of 3.0 using a two-sided McNemar test with a significance level of 0.05. The odds ratio is equivalent to a difference between two paired proportions of 14% which occurs when the proportion of detected missed adenomas during Endocuff-assisted colonoscopy is 21% and the proportion of missed adenomas during conventional colonoscopy is 7%. During one year period before the study initiation, our colonoscopy performance quality data show that we detect a mean number of adenomas per patient equal of 0.7 in a population similar to the one recruited in our study. Therefore, 172 patients overall will be required to detect 120 adenomas. Given the uncertainty of our estimation and in order to cope with patients exclusions, withdrawals and unexpected incomplete colonoscopies, we decided to recruit 200 patients.