The article addresses the problem of intramedullary tumors (IMTs) combined with hydrocephalus (HC). Purpose. The study purpose was to explore, based on large clinical material, the occurrence of hydrocephalus combined with intramedullary tumors, possible pathogenetic mechanisms of its development, effect of tumor resection on the course of hydrocephalus, and need and timing of shunting surgery. Material and methods. We present and analyze the data of the largest individual series of patients of all age groups operated on for IMTs of the spinal cord: 541 patients; 586 operations; age from 2 months to 72 years. Results and conclusion. Our findings confirm a potential pathogenetic relationship between IMT and HC. The overall occurrence rate of HC in IMT patients was 6.3%. In patients with benign tumors (WHO Grade 1―2; 449 patients), HC developed in 25 (5.6%) cases; in patients with malignant tumors (WHO Grade 3―4; 84 patients), HC developed in 7 (8.3%) cases. A statistically significant prevalence of cervico-medullary tumors was found in HC patients: 19 (59.4%) cases. According to our data, dissemination of the tumor process is a potential factor of HC development.