Shoulder arthroscopy is one of the common surgical procedures performed today. After shoulder surgery, providing adequate analgesia is necessary for both the comfort of the patient and the ability to perform the necessary post-operative rehabilitation exercises early and regularly. Nerve blocks reduces opioid consumption in the postoperative period by providing better pain control and therefore has advantages such as fewer side effects and less risk of pulmonary and cardiac complications. In this study; it was aimed to compare the analgesic effectiveness of interscalene brachial plexus block and serratus posterior superior intercostal plane block, with each other and with the control group in the postoperative period in patients who underwent shoulder arthroscopy.