Delusional disorders are divided in French nosography into three clinical disease entities: paranoid delusions, psychose hallucinatoire chronique, and paraphrenia. Their common characteristics are a late start, a chronic evolution, no cognitive impairment and no dissociation. Delusio- nal syndrome is often at the forefront with a predominant mechanism characterizing each disorder (interpretation for paranoid delusions, hallucination for psychose hallucinatoire chronique and imagination for paraphrenia). Although these disorders are less sensitive to the medication than schizophrenia, care is based on second generation antipsychotic treatment, in association with psychotherapy and social care. The aim of treatment is to alleviate delusion intensity to improve global functioning and to prevent violent incidents or suicide attempt.