BACKGROUND: 4-L polyethylene glycol preparations are effective for colon cleansing before colonoscopy. However, large volume and unpleasant taste reduce tolerability and acceptability limiting patient compliance. A new isosmotic low-volume polyethylene glycol preparation with citrates and simethicone plus bisacodyl has been developed to improve patient compliance and tolerability. AIM: To compare the efficacy of 2 different regimens of preparation vs a split-dose of polyethylene glycol solution. PATIENTS AND METHODS: In this randomised, blinded, comparative study, 153 patients were allocated to 3 arms. Arm 1 (n=52) received bisacodyl and 2-L polyethylene glycol with citrates and simethicone the day before the procedure. Arm 2 (n=50) received bisacodyl the day before and 2-L polyethylene glycol with citrates and simethicone on the day of colonoscopy. Control group (n=51) received a split-dose of 4-L polyethylene glycol. Cleansing was evaluated according to Ottawa scale. RESULTS: The mean Ottawa score was not different in the 3 groups. Excellent cleansing was observed more frequently in arm 2 (70%) than in controls (49%) (p<0.05). No serious adverse events were observed in the 3 regimens. The willingness to repeat the same bowel preparation was superior in arms 1 and 2 than in controls (p<0.001). CONCLUSIONS: New low-volume preparations seem to be as effective as the split 4-L polyethylene glycol regimen, showing a better tolerability and acceptability.