Background Supraglottic airway (SGA) devices do not definitively protect the airway from regurgitation of gastric contents. Increased gastric pressure and long operation time are associated with development of complications such as aspiration pneumonia. The aim of this study was to compare intra-gastric pressure between second-generation SGA and endotracheal tube (ETT) devices during long-duration laparoscopic hepatectomy.Methods A total of 66 patients was randomly assigned to two groups; 33 patients each in the ETT and SGA groups. Intra-gastric pressure was continuously measured via a gastric drainage tube with a three-way stopcock connected to the pressure monitoring device. Normal saline was added to the end of the gastric drainage tube at each operation time point.Results Intra-gastric pressure during pneumoperitoneum was no different between the two groups (p = 0.146) or over time (p = 0.094). The mean (SD) pH of the SGA tip measured after operation was 6.7 (0.4), and a pH less than 4 was not observed. Relative risk of postoperative complications was significantly higher in the ETT group relative to the SGA group (sore throat, 5.5; cough,13.0).Conclusions Use of SGA devices does not further increase intra-gastric pressure, even during prolonged upper abdominal laparoscopic surgery. Also, the frequency of postoperative sore throat and cough was significantly lower when the second-generation SGA device was used.Clinical trial registration of Korea (https://cris.nih.go.kr/cris/index.jsp): KCT0003512 Principle investigator: G S K; date of registration February 15, 2019, https://cris.nih.go.kr/cris).