A 52-yr-old man with a residual phase of schizophrenia developed sleep apnoea-hypopnoea syndrome (SAHS). After five days of continuous positive airway pressure (CPAP) treatment, the patient developed an aggressive mood with incoherence, prominent hallucinations and agitation, and attempted to hit his relatives. He was finally admitted to the hospital with an acute psychotic episode. Withdrawal of CPAP, and neuroleptic treatment controlled the episode, and clinical symptoms of SAHS reappeared 10 days later. Schizophrenia associated to sleep apnoea-hypopnoea syndrome has rarely been reported, but, to the authors' knowledge, the induction of a psychotic episode by continuous positive airway pressure treatment in a patient with sleep apnoea-hypopnoea syndrome and coexisting schizophrenia has never been previously reported.