Objective. To elucidate the specific features of diagnostics, clinical course and manifestations of type 2 diabetes mellitus (DM2) in the children of the Russian population. Material and methods. A total of 80 children presenting with DM2 were enrolled in the study including 70 available for the dynamic examination, with the follow-up period of 2.6 years (1.5; 4.5). The general clinical examination of the patients was supplemented by measuring insulin secretion, studying HLA-polymorphism of the DQ and DR-genes, and determination of type 1 diabetes (DM1) — related specific antibodies (At). Results. The median age at diagnosis of DM2 was 13 years (11.5; 15.5). 58.8% of the children had a family history of DM2 but only 26.3% of them had classical complaints of diabetes mellitus. In 65% of the children, DM2 was diagnosed when they were passing medical examination in connection with obesity (in 51.9% with the use the oral glucose tolerance test (OGTP); 48.1% of these children had the fasting blood glucose level above 7.0 mmol/l.  Ketonuria at the onset of the disease was documented in 21.3% of the patients while 85% were either obese or  overweight. Antibodies (ICA and IAA) were detected in 15.2% of the children at a low titer. The HLA-genotype associated with a high risk of development of DM1 was identified in 5.5% of the cases. The glycosylated hemoglobin test revealed its mean level of 7.1% (6.3; 8.5%) at the onset of diabetes; in the majority of the children, it fell down below 6.5% within the first 3 years of the disease. During this period, insulin and C-peptide secretion remained elevated. Insulin resistance was initially documented in 81.3% of the children; the dynamic observation failed to show its appreciable decrease. Insulin therapy initiated at the onset of the disease was prescribed to 30% of the patients. After 3 years, only 8% of the children retaining endogenous insulin secretion continued to use insulin. Conclusion. The asymptomatic onset of type 2 diabetes mellitus in the children and adolescents emphasizes the importance of its active diagnostics during the pubertal period in  the high risk groups comprising the patients with obesity and  the family history of DM2. In one third of the children, the diagnosis of DM2 was possible only with the use the oral glucose tolerance test. DM2 in the children and adolescents is characterized by clinical polymorphism in the form of acute manifestations in 21% of the cases and the absence of obesity and insulin resistance in 15 and 18% respectively. This finding suggests the necessity of differential diagnostics of such cases from DM1 and MODY. Rather high insulin and C-peptide secretion persists for 3 years after the onset of DM2 in the children. Therefore, they do not need insulin therapy during this period. The presence of ICA and IAA antibodies at low titers does not compromise diagnosis of DM2.