Schizophrenia is considered to be a heterogenous disorder. Different etiopathological mechanism can be attributed to a similar clinical picture as described in DSM-III-R criteria. We present a case of a young man diagnosed on different occasions as schizophrenic with mild mental retardation. Clinical examination revealed signs and symptoms most compatible with the diagnosis of Lujan-Fryns syndrome, an X-linked mental retardation syndrome with marfanoid features, frequently associated with psychotic or other psychiatric symptoms. In all patients with symptoms of schizophrenia and mental retardation Lujan-Fryns syndrome should be considered in the differential diagnosis.