Tumors of the ovaries in girls represent an actual problem in modern gynecology. First of all, this is due to diagnostic difficulties, caused by the absence of characteristic complaints, asymptomatic course and the complexity of the gynecological examination, which leads to making of an erroneous diagnosis, the lack of correct and timely treatment and, as a result, complications that often negatively affect the reproductive function of the female patient in further. The differential diagnosis of ovarian tumors in girls is still one of the most important problems of modern practical gynecology. In many patients, the presence of a combined pathology, which is 30-40% according to WHO data, puts the problem of the possibility of simultaneous correction of such pathology by both surgeons and gynecologists. In connection with the difficulty of diagnosing, the diagnosis of such patients must necessarily include an examination of a pediatric surgeon and a children’s gynecologist with ultrasound examination of the retroperitoneal space, abdominal cavity organs, and small pelvis. Errors in the differential diagnosis of genital and extragenital diseases occur quite often and are mainly due to the similarity of clinical symptoms. This article presents a clinical case of the diagnosis and management of a 14-year-old female patient with an adjacent diagnosis, as well as criteria for the diagnostic search for the differential diagnosis of gynecological and surgical pathologies.