In modern neuro-oncology and onco-hematology, intraventricular injection of chemotherapeutic agents (most typically, methotrexate) is an inevitable part of many protocols for treating patients with malignant tumors of the CNS, neuroleukemia, CNS lymphomas and some other disorders. A ventricular catheter system (also known as the Ommaya reservoir) is used to provide repeated injection of chemotherapeutic agents to cerebral ventricles. The use of modern neuronavigation systems allows one to place Ommaya reservoir in patients with narrow and slit-like ventricles. Material and methods. During the period between March 2012 and October 2013, 27 patients underwent stereotactic placement of the Ommaya reservoir using a Cart II optical neuronavigation system (Stryker) at the Dmitry Rogachev Federal Scientific and Clinical Center of Pediatric Hematology, Oncology and Immunology. The patients for stereotactic placement of a ventricular catheter were selected on a subjective basis (small ventricular size was the criterion for selection). In one patient, the surgery for placement of the Ommaya reservoir was combined with stereotactic biopsy. Results. In all patients, a ventricular catheter was placed in the anterior horn of the lateral ventricle on the first try; no intraoperative complications were observed. Conclusions. Frameless navigation is an illustrative, mobile, and multifunctional method. The same device can be used to perform brain, transsphenoidal, ENT, and spine surgeries, as well as orthopedic interventions. Today, neuronavigation systems are used in neurosurgical operating rooms and make it possible to avoid using stereotactic frames in most cases.