Objective. To analyze risk factors for the development of increased blood loss during surgical correction of idiopathic scoliosis. Material and Methods. A total of 395 patients with idiopathic scoliosis were operated on using hybrid instrumentation, in prone position, under inhalation multicomponent anesthesia. Four groups of patients were identified: Group I-blood loss below 15 % of total blood volume (TBV) (n = 201); Group II-blood loss 15-30 % of TBV (n = 133); Group III-blood loss 30-40 % of TBV (n = 42); and Group IVblood loss more than 40 % of TBV (n = 19). In 92 patients, operations were performed under condition of incomplete decompression of the anterior abdominal wall, in 303 patients-under condition of complete decompression. Analysis included data on increased intra-abdominal pressure, the initial condition of the system regulating the aggregate state of blood, the presence of connective tissue dysplasia, and structural features of the bone tissue. Results. Complete decompression of the anterior abdominal wall during posterior instrumental correction allows reducing the volume of intraoperative blood loss by 60 % and avoiding blood transfusion in 75.9 % of patients. Structural and chronometric hypocoagulation associated with the inhibition of lateral aggregation of fibrin, is a start functional state of the hemostasis system in 80.0 % of patients with idiopathic scoliosis. Conclusion. The main importance in solving the problem of reducing the severity of intraoperative blood loss belongs to the correction of the revealed disorders in the system regulating the aggregate state of blood and the implementation of procedures aimed at preventing an increase in intra-abdominal pressure.