Background: The present study was conducted to compare the prevalence and severity of crimes as well as risk factors in crime incidents in two groups of patients with schizophrenia and antisocial personality disorder in order to determine the high-risk group for further preventive approaches.Methods: We have included 74 criminals suffering from antisocial personality disorder and 47 schizophrenia criminal cases, who had been referred during a one-year period by the court in order to receive psychiatric consultation for criminal responsibility. A conformed interview was achieved and a questionnaire was filled including initial data regarding the demographic factors, their victims, type of crimes and the way they had planned. Finally, SPSS software was used for data analysis.Results: The most violent criminals had been attempted by schizophrenic patients (p=0.001). In these patients, there was a significant correlation between crime prevalence and factors like male gender, single hood, noncompliance and financial dependence to the family. In other words their relatives were the major victims of their crimes. However, in patients with antisocial personality disorder unemployment was not a predisposing factor and they mainly committed crime against strangers. These crimes were committed in the early stages of their disorder. Committing crimes 5-10 years later after beginning of their sickness indicated that unemployment was the most important factor made schizophrenic patients does the illegal actions.Conclusion: Patients with antisocial personality disorder commit further crimes; however, schizophrenic patients commit more severe crimes. Trend of schizophrenic patients to their relatives necessitates further family support and patients acceptance by relatives in addition to rehabilitation. Meanwhile, finding a solution for their unemployment could be of great help.