Split dose bowel cleansing is recommended method for colonoscopy. For afternoon colonoscopy, same-day dose of bowel cleansing is alternative option. Recently, same-day bowel cleansing for morning colonoscopy was validated. To date, there was no study which compared the bowel cleansing efficacy between same-day dose and split dose regardless of colonoscopy time. The aim of current study is to compare the bowel cleansing efficacy, adverse events, and patient's tolerability between the two group.