 After introduction of the colonoscope into the cecum, patients will be randomized into withdrawal with either the NBI mode or conventional imaging by using wide-angle colonoscopes with HDTV imaging Olympus Corp., Hamburg, Germany in both groups. Randomization lists will be used for group allocation in each individual practice. In the NBI group, switching back to conventional imaging, and the number of occasions for switching back and the reasons for it are documented in this group. 