All consecutive patients of a population-based colorectal screening cancer program referred for a colonoscopy will be invited to participate in the study. After obtaining informed consent, they will be randomized to one of the groups: liquid diet or low-fiber diet. The will be interviewed by a registered research nurse, and they will be provided with written instructions for bowel preparation and questionnaires for registering the data of the study. The day of the colonoscopy, questionnaires will be collected and endoscopists blinded for the study bowel preparation will perform the colonoscopy. Patients will be contacted for adverse events and a general satisfaction questionnaire, 3 days after colonoscopy.