Available information regarding the clinical features of cannabis-induced psychoses among schizophrenia patients is rather odd and even discrepant. For thorough investigation psychopathology due to marijuana intoxication, we examine two groups of schizophrenia patients. I group--14 patients, who had long history of cannabis use before developing schizophrenia, and II group--schizophrenic patients, who already had schizophrenia and later became marijuana users. Clinical study allowed us to determine the general psychopathological symptoms due to acute intoxication on the one hand, reflecting duration and severity of intoxication, and let us to verify specific mental problems connected to the dynamics of schizophrenia, on the other hand. Peculiar properties of the data of the experimental-psychological tests TAT (Thematic Apperception Test) reflect personality changes generated by schizophrenia progression included the psychopathological phenomenon related to cannabis intoxication. Psychopharmacological treatment brought positive changes in structure and thematic features of the data. The patients used more words. The content and the volume of the stories increased. Trends to improvement were more common for recurrent rather than continuous duration of schizophrenia.