The abuse of flunitrazepam (FZ) compounds is worldwide, and several studies have reflected on the consequences with regard to violence, aggression and criminal lifestyle of FZ users. Criminals take high doses of FZ or some other benzodiazepines to "calm down" before the planned crime. There is support from earlier studies that most likely, all benzodiazepines may increase aggression in vulnerable males. Chronic intake of high doses of FZ increases aggression in male rats. Because psychopathy involves aggression, we have examined whether psychopathy as well as any of the four facets of the Psychopathy Checklist-Revised (PCL-R) (Interpersonal, Affective, Lifestyle and Antisocial) are related to different substance use disorders, with the focus on FZ. We have also examined the relationship between each PCL-R item and FZ use. Participants were 114 male offenders aged 14-35 years, all of whom were convicted for severe, predominantly violent, offences. Substance use, including FZ, was not more common in those who scored high in psychopathy. Use of FZ was more common in offenders who scored high in Facet 4 (Antisocial) of the PCL-R (odds ratio = 4.30, 95% CI 1.86-9.94). Only one of the PCL-R items, "Criminal versatility", was significantly associated with FZ use (odds ratio = 3.7). It may be concluded that intake of FZ has a specific relationship to only one of the facets and not to psychopathy per se. ; The findings have also important theoretical implications because Facet 4 is not a key factor of the construct of psychopathy. Clinical implications of the article: We have used the new two-factor and four-facet theoretical model of psychopathy in the young offender population, many of them with one or more substance use disorders. The present results suggest that antisocial behavior defined by Facet 4 (poor behavioral control, early behavior problems, juvenile delinquency, revocation of conditional release and criminal versatility) in the studied subjects is more typical for FZ users than it is for non-FZ users. This may have implications for assessment and treatment. Clinicians should be aware that criminals with high scores on Facet 4 have a more than fourfold odds of being a FZ user. This conclusion has an important clinical implication because FZ abuse is very common and is not always the focus of a forensic psychiatric assessment. ;