Postoperative pain is important following arthroscopic shoulder surgery. Postoperative effective pain treatment provides early mobilization and shorter hospital stay.Ultrasound (US)-guided brachial plexus blocks such as interscalen and supraclavicular block are usually performed. Interscalene brachial plexus block is one of the most preferred techniques among these. Due to the phrenic nerve paralysis frequently seen in interscalene block, alternative diaphragm-sparing block techniques have emerged over time. One of these is the Infraspinatus teres minor interfascial block. Infraspinatus teres minor interfascial block can block both the suprascapular nerve and the axillary nerve, which are effective in the innervation of the shoulder, with a single-point injection. The main aim of our study was to show that there is no difference between interscalene block and infraspinatus-teres-minor interfascial block in terms of their effects on postoperative analgesia in patients undergoing arthroscopic shoulder surgery.