Type 2 diabetes mellitus is a growing problem in HIV population and a comparison with the general population may help screening and prevention. In this cross-sectional study the authors determined the prevalence of type 2 diabetes mellitus in 4,249 HIV-infected subjects attending the San Raffaele Infectious Diseases Department compared with 9,148 healthy controls recruited in 15 Italian regions, and identified risk factors associated with of type 2 diabetes mellitus. Type 2 diabetes mellitus was defined as reported diabetes, a fasting plasma glucose concentration ≥7.0 mmol/l, or current use of anti-diabetic medication. Prevalence of type 2 diabetes mellitus was higher in HIV-infected than healthy subjects (4.1 vs. 2.5 %; P < 0.0001). At multivariable analysis, HIV-infected subjects (odds ratio 1.70, 95 % CI, 1.12-2.51; P = 0.009), older age (P < 0.0001), higher BMI (P < 0.0001) and hypertension (P = 0.039) were associated with a higher risk of diabetes. Among HIV-infected patients, the risk of type 2 diabetes mellitus increased with older age (P < 0.0001), higher BMI (P = 0.003), higher triglycerides (P = 0.015) lower total cholesterol (P = 0.008), longer duration of HIV infection (P = 0.036) lower nadir CD4 (P = 0.027). Prevalence of type 2 diabetes mellitus in HIV-infected subjects was almost two-fold increased than healthy subjects and it was associated with the typical risk factors of the general population and also to longer duration of HIV infection and lower nadir CD4.