The paravertebral block (PVB) is a well-studied, effective method of analgesia for breast surgery. Alternative techniques involving the blockage of intercostal nerve branches are the serratus anterior plane block (SAPB) and the erector spinae plane block (ESPB). However, no studies comparing both fascial blocks to PVB in breast surgery have been published to date. We evaluated the effectiveness of ESPB and SAPB vs. PVB, expressed as the requirement for intraoperative fentanyl, pain intensity at rest and during coughing, and morphine consumption on the first postoperative day. Additional aims were to perform an evaluation of the safety of the block types used. : A total of 77 women and 1 man with stage I and II clinical breast cancer, aged 18-85 years, were randomized into one of three study groups: SAPB, PVB, and ESPB. There were no statistically significant differences in fentanyl consumption during surgery with respect to the type of block used ( = 0.4246). Morphine consumption in the postoperative period was highest in the ESPB group, averaging 9.4 mg. There was a statistically significant difference in pain intensity from 4 pm on the day of surgery to 8 am the following morning. No complications related to the blocks were observed on the first postoperative day. Both the serratus anterior plane block and the erector spinae plane block were as effective as the paravertebral block in achieving intraoperative analgesia. The serratus anterior plane block was equally as effective as the paravertebral block in achieving postoperative analgesia. The erector spinae plane block was significantly less effective in achieving postoperative analgesia than both the paravertebral block and serratus anterior plane block.