Psychiatric diagnosis, no matter what meaning is assigned to it, deals with a range of behavioral disorders much narrower than the diagnosis of antisocial behaviors. There are few offenders who are mentally disordered, although it is often possible to find mental conflicts or peculiar personality traits in many offenders. Psychiatric diagnosis is grounded in typological, psychopathological, and psychodynamic data; it does not take into account the criminal act that is the main focus of criminological diagnosis. The psychiatrist's main concern in criminology is identifying a given mental illness as the basis for a given criminal act or behavior. Psychiatric diagnosis also has a unique role in criminology in institutional treatment. Any diagnosis related to the development of treatment-offender matching should include psychiatric evaluation. Psychiatric diagnosis is also important before release but is also a further element of discrepancy between psychiatric and criminological diagnostic practices. Psychiatric diagnosis is much more sensitive to prognosis than criminological diagnosis. Overall, psychiatric diagnosis can allow, on the one hand, the inclusion of the criminal act in a defined psychopathological context, while, on the other hand, it can make the criminal act understandable, because it reveals its origin in the complex biography and pathography of the individual. These processes apply particularly to the subjective perception of social norms experienced according to the particular social parameters of the individual. Twenty notes are provided.