Colonoscopy is a very promising screening tool as it allows not only early detection of colorectal cancer but also its prevention by removal of adenomatous precursor lesions. The effectiveness of colonoscopy in reducing colorectal cancer incidence and mortality requires appropriate clearance of the colon from neoplastic precursor lesions. Quality of colonoscopy, measured by adenoma detection rate, depends mainly on the individual colonoscopist’s skills and accuracy. A prerequisite for screening colonoscopy improvement is to be aware of the examination’s quality and to implement continuous quality improvement programmes.