The purpose of this study is to analyse a sample of immigrant forensic psychiatric patients and to compare them with Danish patients. Of the 326 forensic patients in Copenhagen, 111 were immigrants or descendants of immigrants. The sample was broken down according to area of origin, age, gender and ethnic status. The data have been analysed by Poisson regression with the background population as an offset variable. Of the patients of non-Danish ethnicity, a significantly higher ratio was diagnosed with schizophrenia and a lower ratio was diagnosed with personality disorders compared with Danes. Iranians accounted for a higher ratio than did other minority groups, whereas patients from Western Europe/USA were not different from Danes. The higher ratio of forensic schizophrenic patients of non-Danish ethnicity cannot be explained by social factors or substance abuse. Migration increases the age-adjusted risk (ARR) of becoming schizophrenic (ARR=2.7). We found the ARR of becoming a male forensic schizophrenic patient among immigrants/descendants to be 2.8, i.e. the same as that caused by migration as such. Violence and schizophrenia are associated, and this explains the fact that the ratio of immigrants/descendants having committed violence exceeds that of Danes. Non-violent crimes are more equally distributed among ethnic groups and seem to be associated with common criminogenic factors. Arson is mainly committed by older schizophrenic patients of Danish ethnicity. The risk of an individual immigrant and Danish schizophrenic patient exhibiting criminal behaviour is the same. Schizophrenia is a criminogenic factor in violence, but not in non-violent crimes. The differences between the various ethnic groups could be related to selection caused by both immigration and emigration.