Sex offenders are persons convicted for having committed one of a list of statutorily defined sexual offenses. According to the APA Task Force definition, sex offence is a purposeful behavior which involves at least another person, adult or not, in a sexual act with physical, verbal or an other form of coercion or manipulation. A sex offender seems to use the other as an object to achieve his own pleasure, careless of the victim's feelings and suffering. The growing number of sexual abuses and crimes is a social cproblem that claim psychiatric attention, and poses some questions: is this inhuman behavior pathological? are they just cruel, or their cruelty is a symptom of a complex disease? If they've some kind of disease, is there a common dimensional pattern? Answers to these questions open controversial discussions about their psychology, new perspective in treatment and management. The aim of the study is to assess the prevalence of Personality Disorders among sex offenders, referring to a population of convicted in a prison of Genoa, Italy.