Video-assisted thoracic surgery (VATS) has become a common procedure in thoracic surgery. Severe postoperative pain may be encountered in patients undergoing VATS. Analgesic methods such as thoracic paravertebral block (TPVB), intercostal block, serratus anterior plane block (SAPB), and erector spinae plane block (ESPB) are widely used for VATS. Among these methods, ultrasound (US) guided TPVB is the most preferred method. In recent years, the frequency of application of plane blocks as a component of multimodal analgesia has been increased. ESPB and SAPB are some of them. In addition, SAPB application is increasing in patients who underwent thoracotomy and VATS. There is no consensus on the dose of analgesia in these studies. There are studies on volumes between 10 ml and 40 ml in the literature. In this study, it was aimed to compare the volumes of 20 ml and 30 ml containing local anesthetic at the same concentration (0.25% bupivacaine) of SAPB block to be performed with USG in patients who underwent VATS.