Endometriosis is traditionally considered a disease of women of reproductive age and is rarely diagnosed in adolescence, even if there are typical and specific complaints of this disease. However, some studies report that the first symptoms in adult women with endometriosis appeared at the age of 15-16. Due to the low vigilance of pediatric specialists towards endometriosis, the correct diagnosis could be hard to make for 8-10 years. Special attention is paid to the psycho-emotional background of this group of patients: they are more often prone to anxiety disorder, depressive conditions, and self-harm, which are primarily associated with chronic pelvic pain. Ovarian endometriomas are common in 17-44% of adult patients. However, small forms of external genital endometriosis are more common in adolescents. Nevertheless, adenomyosis or endometrioid ovarian cysts can be observed much less frequently than in adults. This article presents a clinical case of a 17-year-old patient with bilateral gigantic endometrioid cysts. 8 months before primary diagnostics the patient noticed periodic pelvic pain for the first time. After a preliminary examination, the patient was taken to the operating room for laparoscopy and cystectomy on both sides. Intraoperatively the right ovary was enlarged to 12 cm and the left one was enlarged to 6 cm. The postoperative period proceeded without complications. The patient was prescribed hormone therapy in the form of combined oral contraceptives after histological confirmation of endometriosis.