OBJECTIVE: Bowel preparation can directly affect the final outcome of a colonoscopy. However, limited studies have been conducted regarding the effect of probiotics on intestinal preparation. Thus, the present study aims to investigate the effect of METHODS AND MATERIALS: In this double-blind, placebo-controlled, randomized clinical trial, 84 colonoscopy candidate pediatric patients were enrolled. Patients were divided into two equal groups of 42 individuals. One group of patients underwent the bisacodyl, polyethylene glycol regimen 48 h before colonoscopy, as along with a placebo. The other group was administered RESULTS: The mean age of patients in the placebo and probiotic groups was 94.1 ± 43.8 and 111.2 ± 48.8 months, respectively ( CONCLUSION: Probiotic pretreatment as part of bowel preparation significantly improves visualization of the colonic mucosa during colonoscopy.