Colorectal cancer (CRC) continues to be a major global disease burden. In 2012, CRC ranked in the third place among the most common malignancies with over 1.3 million new cases and 700,000 annual deaths worldwide. CRC is the third tumour by incidence and mortality among men (respectively 30.0 and 19.9) and the second among women (respectively 21.8 and 11.5). At least 95% of all CRC cases arise from pre-existing polypoid or flat adenomas. Such an adenoma carcinoma sequence provides an opportunity for prevention of colorectal cancers. In principle, screening of CRC can provide possibilities for both i) the primary prevention (i.e., finding pre-cancerous adenomas that could later undergo malignant transformation) and ii) the secondary prevention (detecting early cancers that can be more effectively treated). However, about 3% to 6% of colorectal cancers are diagnosed between screening and post-screening surveillance examinations and the majority of these interval cancers are thought to originate from missed lesions that were overlooked at the screening colonoscopy. According to emerging evidences, the effectiveness of colonoscopy depend on the quality of the examination. High quality bowel cleaning is an essential prerequisite to improve the quality of colonoscopy, because even a small amount of residual fecal matter can obscure a significant colorectal lesion. Rate of adequate bowel preparation is one of main performance measures for lower gastrointestinal endoscopy. Bowel preparation quality assessed using a validated scale such as the BBPS (Boston Bowel Preparation Scale), the Ottawa Scale (Ottawa Bowel Preparation Scale) should be included in every colonoscopy report. ESGE (European Society of Gastrointestinal Endoscopy) published in 2013 year bowel preparation for colonoscopy: European Society of Gastrointestinal Endoscopy (ESGE) Guideline. The ESGE recommends a low-fiber diet on the day preceding colonoscopy. The ESGE recommends a split regimen of 4L PEG solution (or a same day regimen in the case of afternoon colonoscopy) for routine bowel preparation. A split regimen (or same-day regimen in the case of afternoon colonoscopy) of 2 L PEG plus ascorbate or of sodium picosulphate plus magnesium citrate may be valid alternatives, inparticular for elective outpatient colonoscopy. In patients with renal failure, PEG is the only recommended bowel preparation. The delay between the last dose of bowel preparation and colonoscopy should be minimized and no longer than 4 hours. The ESGE advises against the routine use of oral sodium phosphate for bowel preparation because of safety concerns. The ESGE recommends that oral and written information about bowel preparation should be delivered by healthcare professionals. The proposed minimum (≥90%) and target standard (≥95%) rates of adequate bowel preparation. Inadequate bowel preparation results inincreased costs and inconvenience as the examination has to be rescheduled or alternative investigations have to be organized.