Comorbidity of schizophrenia and transsexualism is still controversial. Some authors exclude diagnosis of transsexualism in patients with psychosis others report this coexistence as very rare. Delusions of sex change have been described by some authors in about 20-25% of schizophrenic patients. Patient's “pseudotranssexual” beliefs are usually bizarre and do not cause diagnostic doubts. In some cases complaints of gender dysphoria are predominant and psychotic symptoms can be underestimated or even unnoticed before sex reassignment procedure. Presentation of various clinical manifestation of gender dysphoria in patients with schizophrenia. Three clinical cases are described. Two patients have developed “pseudotranssexual” beliefs during course of psychosis. The first of them is an example of gender identity disorders related to psychotic process. The second patient presented complex psychopathology of schizophrenia and somatic symptoms which can hinder the diagnosis. The third patient has been diagnosed as a transsexual woman after diagnosis of severe schizophrenia and has undergone sex reassignment. Next she was hospitalized several times because relapses of psychosis but also because of alcohol withdrawal. Currently this patient has symptoms of dementia and a few severe somatic diagnoses. The experiences of practitioners indicate that coincidence of schizophrenia and gender identity disorder is possible. Nevertheless, the consequence of misdiagnosis and sex reassignment can be serious and unconvertible. That is why the diagnosis of transsexualism in patients with psychosis should not be made hastily. It needs time, careful observation, examination and cooperation of psychiatrist and sexologist.