PurposeThe aim of this study was to determine whether preoperative body mass index (BMI) was associated with postoperative morbidity after laparoscopic liver resection (LLR) for hepatocellular carcinoma (HCC).MethodsA total of three groups of patients were categorized based on preoperative BMI: low-BMI (≤ 18.4 kg/m2), normal-BMI (18.5–24.9 kg/m2) and high-BMI (≥ 25.0 kg/m2). Baseline clinicopathological characteristics, operative variables, and postoperative 30-day mortality and morbidity were recorded and compared among the three groups. The independent risk factors for postoperative morbidity, including surgical site infection (SSI), were identified using univariate and multivariate analyses.ResultsAmong 226 included patients, 20 (8.8%), 122 (54%), and 84 (37.2%) patients had low, normal, and high BMI, respectively. There were no significant differences in postoperative 30-day mortality rates in patients with low BMI and high BMI compared with those with normal BMI (5% and 1.2% vs. 0%, P = 0.141 and P = 0.408, respectively). However, postoperative morbidity rates were significantly higher in patients with low BMI and high BMI compared to those with normal BMI (40% and 32.1% vs. 17.2%, P = 0.032 and P = 0.020, respectively). According to multivariate analysis, both low and high BMI were independent risk factors of increased postoperative morbidity (OR: 5.03, 95% CI: 1.02–25.6, P = 0.047, and OR: 4.53, 95% CI: 1.75–12.8, P = 0.003, respectively). Low and high BMI were also identified as independent risk factors of increased postoperative SSI rates (OR: 6.25, 95% CI: 1.60–23.8, P = 0.007, and OR: 2.89, 95% CI: 1.04–8.77, P = 0.047, respectively).ConclusionA higher incidence of postoperative morbidity including SSI after LLR for HCC was found in low-BMI and high-BMI patients compared to normal-BMI patients.Clinical trials registrationNot applicable because this is a retrospective observational study.