Оbjective – to estimate the availability of the main anatomical structures of the heart for performing the Cox maze III рrocedure and its modifications through right-sided thoracotomy in the IV intercostal space according to the method of A.Yu. Sozon-Yaroshevich. Material and methods. The experimental study was carried out in the department of pathological anatomy. Right-sided thoracotomy in the 4th intercostal space was performed on 15 corpses that did not have openheart surgery. Measurements were carried out according to the method of A.Yu. Sozon-Yaroshevich using the Bednov angle meter, a metal ruler and a special tool to determine the angle of inclination of the axis of the operating action. The research protocol included four criteria: the depth of the wound, the direction of the axis of the operating action, the angle of inclination of the axis of the operating action, and the angle of the operating action. The fifth criterion is t the availability zone. That criterion was not included in the protocol, since according to the author of the method, the accessibility zone is measured if the bottom of the wound is a large organ. Other criteria were used to investigate the availability of anatomical structures of the heart for surgery: the right atrium, the appendage of the right atrium, coronary sinus, tricuspid valve, left atrium, left atrial appendage, right pulmonary vein collector, left pulmonary vein collector, and mitral valve. Results. In total, 8 corpses of men and 7 corpses of women were examined. Average height 172.0 ± 8.2 cm, weight 79.1 ± 9.3 kg. The tilt of the axis of the working action for the right heart made it possible to perform surgical manipulations. When the right atrial appendage was stretched, the tilt of the axis of the working action made it possible to carry out operations on the left atrium and left atrial appendage, mitral valve and pulmonary veins without hindrance. The depth of the wound for access to the main anatomical structures of the heart had acceptable values; the maximum depth of the wound fell on the left collector of the pulmonary veins (mean value 15.2 ± 2.6 cm). The angle of the working impact / the angle of inclination of the axis of the working impact were maximum to the right atrium and to the appendage of the right atrium (mean value 75 ± 3°/ 81 ± 3°), and the minimum – to the collector of the left pulmonary vein (mean value 41 ± 3°/63 ± 4°). Based on the four main criteria according to the method of A.Yu. Sozon-Yaroshevich, mini access through a rightsided thoracotomy can be used for the Cox maze III рrocedure, but if the patient has no absolute contraindications. Conclusions. Access through a right-sided thoracotomy in the 4th intercostal space allows performing full surgical manipulations on the necessary anatomical structures of the heart during the Cox maze III рrocedure and its modifications.