Endoscopic screening is the main method of colon examination. An important factor for the accurate diagnosis of various pathological changes in the mucous membrane of the lower part of the digestive tract is the degree of its visualization, which directly depends on the quality of preparation for colonoscopy. There are many colon cleansers, but the peristaltic motion of the gut slows down in various diseases and syndromes, which results in the reduced accuracy of endoscopy.The paper presents the analysis of colon preparation quality using Phospho-soda (Casen Recordati, S.L., Spain) for colonoscopy in 198 patients with pathological conditions that impedes passage of all bowel contents: inflammatory bowel disease, acromegaly, and hypotonia of the large intestine. The authors carried out a comparative analysis with a control group, which included 106 patients without factors that slowed down the peristaltic motion of the intestine, who were preparing for endoscopic examination according to a similar scheme.The study showed that using Phospho-soda to prepare for endoscopic examination in patients with decreased colonic tone resulted in the efficacy of the drug comparable with its efficacy in a group of patients without dysmotility.