OBJECTIVE The aim of the present study was to investigate the effect of ultrasound-guided bilateral posterior quadratus lumborum block (QLB) and lateral QLB on postoperative pain scores after laparoscopic cholecystectomy. METHODS In this prospective, randomized, single-blind study; 60 patients with elective laparoscopic cholecystectomy operations were randomized into two groups as group P (n= 30): Posterior Quadratus Lumborum Block + IV patient-controlled analgesia (PCA) tramadol and group L (n= 30): Lateral Quadratus Lumborum Block + IV PCA tramadol. Primary outcome measures included the amount of total consumption (24 hours) of tramadol. Secondary outcome measures; Visual Analog Scala (VAS) scores at rest and on movement (postoperative 30th minute, 2nd, 6th, 12th, and 24th hours) were recorded. Adverse effects (nausea and vomiting), additional analgesic requirement, and intraoperative opioid requirement were recorded. RESULTS Postoperative total consumption amounts of tramadol and VAS scores (rest and on movement) were compared, and there was no statistically significant difference between the two groups (p> 0.05). There was no statistically significant difference in adverse effects (nausea and vomiting), additional analgesic requirement, and intraoperative opioid requirement between the two groups (p> 0.05). CONCLUSIONS Similar postoperative tramadol consumption values and VAS scores were determined in both lateral QLB and posterior QLB block applications in the results of our study.