The aim of this study was to compare different end-tidal carbon dioxide (EtCO2) levels to prevent postoperative nausea and vomiting (PONV) caused by increased intracranial pressure due to pneumoperitoneum and Trendelenburg position in gynaecological laparoscopic surgery. A total of 60 female patients aged 25-50 years who would undergo laparoscopic gynaecological surgery under general anaesthesia were randomised into two groups: group A (EtCO2: 26 - 35 mmHg,n = 30) and group B (EtCO2: 36 - 45 mmHg,n = 30). In both groups, ONSD and EtCO(2)of the patients were measured at baseline after anaesthesia induction (T-b), at 5 min after pneumoperitoneum (T-PP5), and at 10 min intervals after Trendelenburg position (T-PP10,T-PP20,T-PP30). At 5 (T-D5) and 10 min (T-D10) after deflation, ONSD measurements were repeated. The incidence and severity of PONV of the patients, and antiemetic drugs used in both groups were assessed in the postoperative period. In the intraoperative follow-up periods,T(PP5)and subsequent EtCO(2)values, as well asT(PP10)and subsequent ONSD values, were significantly higher in group B and the incidence of nausea, the PONV scores and the incidence of rescue antiemetic use significantly lower in group A than in group B (p<.001 for all). This result indicates that low EtCO(2)levels have beneficial effects on ICP and PONV in laparoscopic gynaecological operations.Impact statement What is already known on this subject?Laparoscopic gynaecologic surgery has been a more preferred technique. The incidence of postoperative nausea and vomiting (PONV) after laparoscopic gynaecologic surgery is remarkably high. In the prevention of PONV after gynaecologic laparoscopic surgery, single and multiple drug therapies and methods have been used. Whatthe results of this study add?Postoperative nausea and vomiting caused by intracranial pressure (ICP) increase due to carbon dioxide pneumoperitoneum and Trendelenburg position in gynaecologic laparoscopic surgeries were decreased in the early postoperative period by low end-tidal carbon dioxide levels in the intraoperative period. It was shown that low end-tidal carbon dioxide levels have beneficial effects on ICP and PONV in laparoscopic gynaecologic operations. Whatthe implicationsareof these findings for clinical practice and/or further research?This result indicates that low end-tidal carbon dioxide levels have beneficial effects on ICP and PONV in laparoscopic gynaecologic operations.