The aim of our study was to determine the development of the number of patients with schizophrenia in detention (section 63 German Penal Code) in North Rhine-Westphalia and the characterization of these patients. Patients with schizophrenia are examined, by using a standardized questionnaire answered by the attending psychiatrist or psychologist (n = 531). During the last 12 years the number of patients with schizophrenia in forensic-psychiatric hospitals has increased three times, whereas the number of patients with other diagnoses heightened only twofold. The patients with schizophrenia showed high rates of psychiatric comorbidities (substance disorders 73.9 %, personality disorders 17.2 %), previous inpatient treatments (78.3 % with a mean of 7.5 stays) and previous convictions (63.4 %). Almost half of these convictions (46.6 %) were violent offences (e. g. assault, homicide). Possible explanations for this development are discussed.