The clinical and social pathomorphism of mental and behavioral disorders due to the use of psychostimulants and cannabinoids actualized the problem of diff erential diagnosis and therapy of these patients. The most popular among young people are cannabinoids (including synthetic cannabinoids), psychostimulants and hallucinogens. In clinical practice, intoxication psychoses are more and more common due to the use of psychoactive substances, often occurring as schizophrenic-like disorders, which entails the diffi culties of diff erential diagnosis with endogenous disorders. The relevance of the "problem of psychotic potential" of psychostimulants is also due to the discussion about the advisability of medical use of cannabinoids in a number of serious diseases. The article describes the clinical picture and dynamics of the development of psychotic disorder due to the combined (cannabinoids, psychostimulants, hallucinogens) substance abuse. The presented clinical analysis and diff erential diagnosis between psychotic disorders due to substance abuse with schizophreniform symptoms and psychoses of endogenous origin (schizophrenia, bipolar affective disorder. The relevance of this case is the similarity of the clinical picture with endogenous disorders and the resulting diagnosis diffi culties, differential and treatment of these disorders. The article discusses aspects of the use of second-generation antipsychotic drug olanzapin (Egolanza) in the treatment of psychotic disorders of exogenous etiology.