This study investigated the associations of psychopathy and substance use disorders (SUDs) with criminal offending among 202 men with schizophrenia and 78 men with a primary diagnosis of psychopathy. Comparisons among six groups of offenders indicated that non-mentally ill offenders diagnosed with psychopathy committed the highest numbers of offenses per year at risk. Among offenders with schizophrenia, those with high psychopathy scores committed more crimes than those with low psychopathy scores. Among non-mentally ill offenders with psychopathy and schizophrenic offenders with high psychopathy scores, those with and without SUDs committed, on average, similar numbers of offenses. These findings Suggest that among offenders with psychopathic traits, the traits, not substance abuse, are associated with criminal offending.