© 2020 International Association of Oral and Maxillofacial SurgeonsThis study sought to determine the rate of sinus membrane perforation in patients undergoing crestal sinus grafting, as well as the effect of Schneiderian membrane thickness and residual bone height (RBH) on membrane perforation, using cone beam computed tomography. The study included 25 patients undergoing 44 crestal sinus grafting procedures. The sites for crestal sinus grafting were divided into a control group (RBH ≥ 5 mm) and a test group (RBH < 5 mm). All sinus grafting procedures were also categorised based on membrane thickness: group A (<1 mm), group B (1–2 mm), and group C (≥2 mm). The rate of membrane perforation was 18.2%. The median RBH measurement was 5.59 mm. No statistically significant difference in membrane perforation rate was found between the test and control groups (P = 0.262). The median thickness of the Schneiderian membrane was 1.35 mm. There was no statistically significant difference in membrane perforation among the three membrane thickness groups (P = 0.431). No significant correlation between RBH and membrane perforation was observed, although clinical observation indicated that there was a tendency for an increased membrane perforation rate in the presence of a RBH < 5 mm. The perforation rate was found to be at its highest when the membrane was thinner than 1 mm.