Colorectal cancer remains the third most common cause of death from cancer worldwide. The adenoma detection rate is correlated with quality of colonoscopy and risk of postcolonoscopy CRC. Low quality of bowel preparation with fecal residue and brown liquid in the colon may lower the adenoma detection rate (ADR). Optimal bowel preparation and novel approaches for colonoscopy increases the effectiveness of colonoscopic examination to improve ADR are desirable. Water exchange, which significantly increased colon cleanliness both in the right colon and the entire colon, is characterized by insertion to the cecum in clear water in lieu of gas insufflations. Water exchange led to an increase in ADR, particularly for the improvement in the right colon, providing adequate bowel preparation. NBI is an innovative imaging technology which efficiency for the early detection of superficial cancers in the head and neck region and the esophagus had been reported previously. In the colorectal region, different results have been reported for improvement in the adenoma detection rate of NBI compared with that of WLI. All procedures were performed up to the cecum by using a high-definition colonoscope (GIF-HQ290I; Olympus Optical ) However, whether NBI in high-definition colonoscope can increase the ADR after water exchange insertion, remains to be elucidated. The aim of this study was therefore to determine whether the use of NBI system as an adjunct to water exchange insertion would improve the ADR