The aim of this study was to evaluate the effects of intraperitoneal and extraperitoneal CO2 insufflation on blood gases during and after laparoscopic surgery. Forty patients were included in this study. Twenty patients underwent elective laparoscopic cholecystectomy with intraperitoneal insufflation (intraperitoneal group) and 20 patients underwent laparoscopic inguinal hernia repair with extraperitoneal insufflation (extraperitoneal group). Arterial blood gases were analyzed at four points: 10 minutes after induction, 10 minutes after insufflation, 10 minutes after desufflation, and 30 minutes after the operation in the recovery room. PaCO2 values in the intraperitoneal group at the four points were 36.8 +/- 4, 39.6 +/- 5.9, 40.7 +/- 4.4, and 42.3 +/- 4.8 mm Hg; in the extraperitoneal group, 35.8 +/- 3.9, 37.4 +/- 4, 42.8 +/- 6.6, and 46.2 +/- 5.9 mm Hg. In the extraperitoneal group, there was a significant increase in postoperative PaCO2 compared to the desufflation PaCO2. In our study, extraperitoneal CO2 insufflation caused increases in PaCO2 values that started perioperatively and continued in the postoperative period.