BACKGROUND A complete cleansing of the bowel is a critical factor that impacts the diagnostic accuracy of colonoscopies. However, the common bowel preparation regimen of two 45 mL doses of sodium phosphate (2×NaP) often leads to uncomfortable symptoms and subsequently lower patient adherence. To improve patient adherence and satisfaction, we proposed a modified regimen composed of two sennoside tablets and one bottle of NaP (S+NaP) and we then evaluated bowel preparation quality and patient satisfaction. MATERIAL AND METHODS A total of 531 patients who underwent colonoscopies at the outpatient coloproctology clinic from January 2016 to December 2016 were retrospectively reviewed. Eligible patients were divided into two groups: S+NaP group (n=93) and 2×NaP group (n=60). We compared bowel preparation quality, adenoma detection rate (ADR), self-reported patient satisfaction scores, and adverse events among the two groups. RESULTS Regarding high bowel preparation quality, our results showed that there was no significant difference among the two groups (p=0.775), as well as no significant differences in ADRs (p=0.187). However, a lower proportion of nausea was found in the S+NaP group compared to the 2×NaP group (24.7% versus 41.7%, respectively, p=0.028). In addition, patients in the S+NaP group were more likely to be very satisfied with the regimen compared with patients in the 2×NaP group (odds ratio: 5.58; 95% confidence interval: 2.36-13.213, p<0.001). CONCLUSIONS Our modified bowel preparation regimen, S+NaP, yielded significantly higher patient satisfaction with less nausea while maintaining similar bowel preparation quality.