Questions remain about the relationship between type 2 diabetes mellitus (type 2 DM) and the risk of hepatocellular carcinoma (HCC), especially in patients with chronic liver diseases. We carried out a meta-analysis of cohort studies to explore these issues. We searched PubMed and EMBASE for studies on the association between type 2 DM and the risk of HCC through 30 September 2013. We included patients with chronic liver diseases. Summary relative risks with their corresponding 95% confidence intervals (CIs) were calculated using a random-effects model. A total of 21 cohort studies with 24 reports were included in our analysis. After a median duration of follow-up of 6.4 years, a total of 2528 HCC cases were identified in 35 202 participants. The summary relative risk of HCC with type 2 DM was 1.86 (95% CI 1.49-2.31) for patients with chronic liver disease, 1.90 (95% CI 1.37-2.63) for patients with hepatitis C virus infection, 1.93 (95% CI 1.35-2.76) for patients with cirrhosis, and 1.69 (95% CI 0.97-2.92) for patients with hepatitis B virus infection. Subgroup analyses indicated that the positive associations were independent of geographic location, duration of follow-up, and confounding factors such as smoking, alcohol use, and body mass index (BMI). Hepatitis C virus-infected or cirrhotic patients with the concomitant presence of type 2 DM would have a higher risk of developing HCC than those without DM. Therefore, these patients require more active monitoring of the development of HCC.