Introduction. Extraorgan cysts of the retroperitoneal space (ECRS) remain a challenge in terms of determining therapeutic and diagnostic tactics. In most cases, ECRS are asymptomatic, which explains their detection as an incidental finding during examinations or surgical interventions in the abdominal cavity and/or retroperitoneal space. The main method for treatment of true and formed false ECRS consists in surgery with both laparotomy and laparoscopic accesses. Materials and methods. Clinical case: patient M., female, 39 years old, addressed to one of the clinics in Ufa with complaints of periodic lower left abdominal pain. Based on the results of the examinations, a diagnosis was made of a large tumor of the left ovary, complicated by pain. Concomitant diagnosis: multinodular uterine myoma. Surgical treatment — conservative myomectomy — with laparotomy access was performed due to the large size of the neoplasm. Intraoperatively, in the left iliac region, a volumetric liquid formation measuring 20×15 cm, not associated with the ovary, was discovered retroperitoneally. After further examination, the patient was referred for surgical treatment for retroperitoneal tumor in the City Clinical Hospital No 21. Results and discussion. The surgery was performed laparoscopically. The duration of the surgical intervention accounted for 39 minutes. The postoperative period was reported to be uneventful. Drains were removed on the second day. The patient was discharged from hospital on the fifth day after surgery. Histological examination of the cyst wall revealed no epithelial lining; the wall consisted of fibrous tissue. In this clinical case, according to the results of histological examination, the structure of the cyst wall corresponds to the secondary type or false cysts due to no epithelial lining. Conclusion. In cases of extraorgan retroperitoneal cysts, laparoscopic excision is considered to be a safe and effective method with less postoperative pain and a shorter recovery period compared to open interventions.