Objective. To explore an effect of premorbid functioning level on the efficacy of psychosocial therapy in adolescents with schizophrenia spectrum disorders in order to determine a differential approach to its performance. Material and methods. A study included 53 adolescents with schizophrenia spectrum disorders at the early stage of remission achievement (PANSS scores <65). An impact of premorbid functioning was assessed with the DD-CGAS and the efficacy of psychosocial therapy with CGAS and PedsQL at baseline and after 3, 6 and 12 months. Results and conclusion. We described the most relevant differences in characteristics of treatment effect (dc) between three groups with different levels of premorbid functioning. To increase the efficacy of psychosocial interventions, we suggest a differential approach of psychosocial therapy in each group.