The objective. To assess the influence of paraportal and peripheral localisation of an endometriotic ovarian cyst on ovarian reserve and the quality of life of patients. Patients and methods. The study included 100 patients with monolateral endometriotic ovarian cysts with sizes from 2 to 8 cm and chronic pelvic pains associated with external genital endometriosis. Two groups were singled out: group 1 consisted of 30 patients with paraportal localisation of the cyst and chronic pelvic pain; group 2 – 70 patients with peripheral localisation of an endometriotic cyst and chronic pelvic pain. The control group comprised 30 patients with preserved reproductive function without ovarian cysts. Ovarian reserve was assessed by ultrasound and hormonal examinations including antral follicle count, power Doppler imaging with vascularisation (VI) and flow indices (FI), anti-Mullerian (AMH) and follicle-stimulating hormone (FSH) testing. The intensity of chronic pelvic pains was assessed by the Biberoglu and Behrman scale. Laparoscopic surgery was performed, paraportal or peripheral localisation of the cyst and the firmness of capsular attachment were confirmed intraoperatively. Results. In patients with endometriotic cysts a decrease of ovarian reserve by 22–50% was found as compared with women from the control group: AMH – 36%, FSH – 37.4%, AF – 50%, VI – 43%, FI – 22.7%. Examination of ovarian reserve in patients with paraportal location of endometriomas found its significant decrease and a more marked intensity of chronic pelvic pains as compared with the results in case of peripheral localisation of a cyst. Conclusion. Paraportal localisation of an endometriotic cyst conditions a more significant decrease of ovarian reserve as compared with its peripheral localisation. In paraportal localisation of an endometriotic cyst the quality of life decreases to a greater extent due to more intense chronic pelvic pain. © 2019, Dynasty Publishing House. All rights reserved.