The study aimed to compare the accuracy of end-tidal carbon dioxide partial pressure (PETCO2) and transcutaneous carbon dioxide partial pressure (PTCCO2) to predict arterial carbon dioxide pressure (PaCO2) in patients scheduled for retroperitoneoscopic urologic surgery. Fifty patients undergoing retroperitoneoscopic urologic surgery under general anesthesia were included. Values of PaCO2, PETCO2, and PTCCO2 were obtained before and 30, 60, 90 minutes after pneumoperitoneum. The difference of PaCO2 - PETCO2 and PaCO2 - PTCCO2 was calculated. We performed a correlation and regression analysis between PaCO2 and PETCO2, as well as between PaCO2 and PTCCO2. Additionally, Bland-Altman analysis evaluated the agreement between PaCO2 and the other two variables. The absolute difference of PaCO2－PETCO2 was 13.20 ± 4.43 mmHg and 4.35 ± 2.56 mmHg for PaCO2－PTCCO2 (P < 0.0001). And the correlation coefficient between PaCO2 and PETCO2 was 0.79 (r2 = 0.62, P < 0.0001), whereas that value between PaCO2 and PTCCO2 was 0.91 (r2 = 0.83, P < 0.0001). The 95% limits of agreement of PaCO2 versus PETCO2 was 4.53 to 21.88 mmHg and -3.18 to 10.48 mmHg for PaCO2 versus PTCCO2. These findings indicate PTCCO2 monitoring provided greater accuracy to estimate PaCO2 in patients undergoing retroperitoneoscopic urologic surgery.