Although ADHD (attention deficit hyperactivity disorder) is one of the most common psychiatric disorders in children, much less is known about its prevalence among adults (where the clinical picture may vary), and it is almost never diagnosed in adult psychiatry. The article consists in a report showing the disorder to have been a common finding in a group of prison inmates, and to have been characterised by strong relationships with a series of other psychiatric disorders (e.g. anxiety and personality disorders) with the presence of self-reported anomalous alcohol reactions, and with the degree of criminality. Current diagnostic practice is unfortunate, partly due to the risk of overdiagnosis of anxiety and personality disorders, and partly due to the risk of missing a condition possibly amenable to treatment.