Adequate bowel preparation is the key of a successful colonoscopy. The aim of the study was to analyze sociodemographic and clinical characteristics in our population of patients referred for colonoscopy. Bowel cleanness was evaluated using the Boston Bowel Preparation Scale (BBPS) where values 7 were considered a criterion of successful bowel preparation. The study involved 286 subjects (61.5% male, median 61 years, interquartile range 50-71). BBPS score 7 was found in 145 subjects (50.7%). Multivariate analysis indicated that subjects with severe comorbidity (ASA status 3, OR = 0,29; 95% CI: 0.12-0.72; p = 0,008) represented a risk factor for poor bowel preparation. Regimens with polyethyleneglycol (PEG) were superior compared with other protocols (OR = 2.54; 95% CI: 1.27-5.10; p = 0.008). Timing of the colonoscopy also contributed to better bowel preparation (OR = 5.50; 95% CI: 2.07-14.67; p = 0.001). This study confirms that presence of comorbidity and non-use of PEG regimens are predictors of poor bowel preparation in our population of patients referred for colonoscopy.