Aim. To study the rheological properties of blood and platelet hemostasis in children with inflammatory bowel diseases before and after a course of hyperbaric oxygenation Materials and methods. Aggregation and deformability of erythrocytes, activation and aggregation of platelets were studied in 16 patients with Crohn's disease and 11 patients with ulcerative colitis age from 6 to 17 years. Similar indicators were studied after a course of hyperbaric oxygenation, carried out in a single-seat air-oxygen pressure chamber “BaroOx 1.0”. The course consisted of 5-8 daily sessions in the 1.3-1.4 ata during 40 minutes. Results. In pediatric patients with Crohn's disease and ulcerative colitis a significant violation of the rheological and hemostasiological properties of blood was revealed. After a course of hyperbaric oxygenation a significant decrease in the aggregation of erythrocytes, an increase in their deformability, and a decrease in the functional activity of platelets were noted. Conclusion. The use of hyperbaric oxygenation in children with inflammatory bowel diseases contributes to a significant correction of the rheological and hemostasiological properties of blood.