The goal of the study was to estimate the prevalence of current and lifetime mental disorders in a consecutive sample (n=300) of detainees and prison inmates held in an Italian prison and compare it with the prevalence observed in a sample randomized from the community (n=300) within the same age interval (18-55 years) and sex proportion of prisoners, and with a similar socio-economic status. Psychiatric disorders were identified with the Mini International Neuropsychiatric Interview (MINI). Current psychiatric disorders were present in 58.7% of prisoners and 8.7% of the comparison group. Lifetime psychiatric disorders were present in 88.7% of prisoners and 15.7% of the comparison group. Current anxiety disorders and current stress-related disorders were related to prisoners serving their first-ever prison sentence. A variable fraction of prisoners with an ongoing psychopathology is not diagnosed or does not receive proper treatment. The provision of effective treatment to prisoners with psychiatric disorders might have potentially substantial public health benefits. (C) 2014 Elsevier Ireland Ltd. All rights reserved.