The aims of the present study were to assess the prevalence and comorbidity of psychiatric disorders in subjects with intentional drug overdose and to explore whether there were gender differences in prevalence and comorbidity. A standardized psychiatric evaluation was performed in 100 randomly selected subjects, 18 years old and older, with intentional drug overdose referred to an emergency department. The prevalences of psychiatric morbidity and comorbidity were very high in both genders: 88% presented with at least one psychiatric diagnosis, and three-quarters presented with comorbid psychiatric disorders. Affective and anxiety disorders were the most prevalent diagnoses. One patient out of three presented with alcohol or substance misuse. Compared to females, males suffered five times more often from substance misuse and three times more often from psychotic syndrome and were three times less likely to present with anxiety disorder. When subjects are referred to hospital for intentional drug overdose, medical management should systematically involve a psychiatric assessment in order to identify not only affective and anxiety disorders, but also alcohol and substance misuse, due to the high prevalence of these disorders, especially in male subjects.