Relevance. Auto-aggressive harming behavior (ASB) among children and adolescents who suffer from mental disorders of various nosologies is an urgent problem and requires a special approach from the diagnosis and rehabilitation of such patients. Purpose: To identify clinical, pathopsychological and neurophysiological characteristics of ASP in children and adolescents with different etiopathogenesis depending on the manifestation within the framework of ASD and nosologies of the schizophrenic range with affective disorders. Materials and methods. The study included patients being treated in the Department of Child Psychiatry Study of the Federal State Budgetary Institution National Center for Mental Health. Two samples of patients were formed: the first sample included 30 patients (23 boys and 7 girls), the average age was 6.9 ± 2.5 years, with diagnoses according to ICD-10 ‘Childhood autism’ (DA, F84.02), ‘Atypical autism with mental retardation’ (AA with mental retardation, F84.11), ‘Atypical autism without mental retardation’ (AA without mental retardation, F84.12) with the presence of psychotic symptoms during an attack. The second sample consisted of patients with signs of nonsuicidal ASP (with traces of bodily self-harm) with moderate and severe severity within the nosologies of the schizophrenic circle. 25 female children and adolescents were examined, the average age was 14.15±0.95 years, with diagnoses according to ICD-10 of ‘Schizoaffective disorder, depressive type’ (F25.18), ‘Pseudopsychopathic schizophrenia’ (F21.4), ‘Undifferentiated schizophrenia, observation period less than a yea’ (F20.3). Research methods included clinical-psychopathological, pathopsychological, and neurophysiological studies (EEG with spectral analysis and topographic mapping), survey data with psychometric scales. Results. In patients of the 1st sample with ASD, the leading syndrome in the structure of psychosis was catatonic. Self-harm varied in clinical presentation and severity. In 16 (53%) people, self-harm was represented by palm strikes to the head and face, 11 (37%) – hitting the head against various surfaces, 6 (20%) – hitting parts of the body with the palms, and 6 (20%) – biting fingers and hands. The severity of clinical manifestations of ASP in children with ASD corresponded to the data of a psychometric examination: the severity of autism on the CARS scale was 54.3 ± 3.1, according to the general catatonia scale (BFCRS, Bush-Francis Catatonia Rating Scale, 1996) was 32.7 ± 2.5, which corresponds to a ‘severe’ degree of catatonic disorders. A pathopsychological examination of children with ASP within the framework of ASD revealed a delay in psycho-speech development with signs of the formation of a cognitive defect against the background of distorted dysontogenesis with dissociation of cognitive activity, autism, stereotypic behavior, heteroaggression and ASP, emotional flatness and pronounce dnegativism. These children howed diffuse changes in the form of an increase in the level of slow-wave θ activity, which can be considered as an EEG correlate of immaturity, acuity, and regression of mentalfunctions. Behavioral disorders in the second group of patients with nonsuicidal ASP manifest themselves within the nosologies of the schizophrenic circle (F25.18, F21.4, F20.3), occurring with hallucinatory-delusional, psychopathic-like, and negative symptoms of varying severity, against the background of moderate or severe episode with antivital manifestations, without suicidal actions. Often (in 64% of the patients), the course of the underlying disease was accompanied by cognitive deficits with impaired thinking and memory. The total score on the PANSS scale was 102.5 points, on the CGI scale 6-7 points, which corresponds to a pronounced and severe degree of psychopathological symptoms. Pathopsychological analysis in these patients revealed a dissociated type of mental development, a diversity of thinking, disturbances in the form of slips, associations with secondary symptoms, deficits of will and emotions, and disturbances in social functioning. The decrease and disorganization of the α-rhythm and the increased β-rhythm revealed on the EEG were considered assigns of suppression of the activity of the functions of the cerebral cortex and the severity of psychopathological disorders; the dominance of slow θ- and δ-rhythm sindicates the dysontogenesis of mental development with dissociation of cognitive activity and the formation of cognitive deficit.