Background. Paraovarian/paratubar cysts (PO/PT) is about 5-20% of the cystic formations of uterine adnexes. As usual, these formations meet in the third and fourth decades of life. Paraovarian or paratubar borderline tumors are rarely registered. A limited number of communications on these cases are published in foreign literature. Considering the extreme rarity of paraovarian borderline tumors, we present our own clinical case Case report. The 15-year-old patient M.C. was hospitalized in the surgical gynecology department in connection with the detection of ovarian cyst on the right side. She accuses moderate pain in the lower abdomen. Above bladder, at palpation there are a volume formation of about 10 cm. At USG examination: in the right ovary projection were detected a cystic formation of 103×94×87 mm (volume – 440.5 cm3), with nonhomogeneous content, with parietal vegetation on insertion wide basis, up to 38 mm, non-vascularized. Values of oncological markers: CA-125 – 34.5 U/ml (reference: 0-35 U/ml); CA-19.9 – 35.9 U/ml (reference: 0-33 U/ ml); CEA – 1.3 ng/mL reference: 0-6 ng/mL); α-fetoprotein – 0.7 IU/mL (reference 0-7 IU/mL); anti-Mullerian hormone (AMH) – 1.8 ng/mL. Phannenstiel transverse incision surgery was performed: in the paraovarian region, on the right, was determined a cystic formation, hard-elastic, diameter of about 10 cm, that did not affect the ipsilateral ovary, but involved the uterine tube. The preparation was exuded in the plaque and the tumor was extirpated, with the ovary ptreservation. Because of the concretion of the capsule with the posterior side of the ligamentum, the attempt to keep the uterine tube failed and the decision was made to perform tubectomy. The postoperative period was without any particularities, the patient was discharged on the 5th postoperative day. The histological examination revealed the morphological peculiarities of a papillary cystadenoma at the limit of malignancy or, more preferably, of the borderline type, serous. Twenty-one months after surgery, the patient remained asymptomatic. Conclusions. The clinical case presented is the fourth case of paraovarian/paratubar borderline tumor in pediatric patients, documented in the literature at that time. Ovarian conservation, with maximum preservation of fertile function, are currently the unanimously accepted tactics.