Introduction. Cytoreductive surgery in patients with advanced ovarian cancer often involves extensive combined surgical interventions, which can affect the development of postoperative complications.Aim. To evaluate the results of surgical treatment in patients with advanced ovarian cancer.Methods. The study included 190 primary IIB–IV stage ovarian cancer patients who underwent surgical treatment in the oncogynecological department of the National Medical Research Centre of Oncology n. a. N. N. Petrov (Saint Petersburg, Russia) from August 2017 to August 2020. The dissemination in the peritoneum was assessed by calculating the peritoneal carcinomatosis index (PCI). Surgical complexity score was assessed using Aletti’s classification. Analysis of postoperative complications was carried out in accordance with the Clavien – Dindo classification.Results. The incidence of postoperative complications depended on the index of surgical complexity score (5 % – with a low index, 15 % – with median, 63 % – with a high one, p < 0.0010). In the group of primary cytoreductive surgeries, cases of median (48.9 %) and high complexity score (24.44 %) prevailed; in the group of interval debulking surgery, cases of low (52.4 %) and median (36.5 %) complexity score prevailed. The index of surgical complexity score depended on the peritoneal carcinomatosis index (PCI). The operation time, the volume of blood loss, the duration of hospitalization, frequency of bowel resection depended on the peritoneal carcinomatosis index and the surgical complexity score (p < 0.0001).Conclusions. The level of surgical complexity score in patients with advanced ovarian cancer depends on the peritoneal carcinomatosis index. The level of surgical complexity score is higher in the group of primary debulking surgery, which effect on frequency of postoperative complications.