Down syndrome (DS), acommon genetic disorder, leads to various physical, cognitive, and developmental challenges. The supplementary copy of chromosome 21 introduces an abundance of genes, which potentially can influence metabolic irregularities. The aim of the study is to conduct acomprehensive comparative assessment of oxidative stress indicators (TAS, TOS, OSI), BMI, fasting glucose, and insulin levels, HOMA-IR among children and adolescents with DS in contrast to their non-DS siblings. and the control group (CG) comprised 20 individuals, siblings of SG (mean age 15.92 years). Anthropometric measurements were conducted. TAS, TOS, fasting glucose, and insulin were assessed. BMI, BMI SDS, OSI and HOMA-IR were calculated. SG vs. CG: BMI - overweight (29,19% vs. 15%), obese (19,05% vs. 5%); TAS (1.92 mmol/l vs. 1.79 mmol/l (p=0.0015)); TOS (51.52mmol/l vs. 33.05 mmol/l (p=0.014)); OSI (2475.02 vs. 1949,75 (p=0.038)); no significant differences in fasting glucose, insulin and HOMA-IR. Statistically significant correlations in SG: TOS and BMI, BMI SDS, HOMA-IR; OSI and BMI, BMI SDS, HOMA-IR; HOMA-IR and BMI SDS; fasting insulin and BMI PC; in CG: TAS and BMI; fasting glucose and fasting insulin. The research results indicate differences in metabolic processes between the group of individuals with DS compared to the CG, despite shared environmental conditions. The presence of an additional copy of chromosome 21 may contribute to the occurrence of metabolic disorders. These findings emphasize the need for further research that will lead to abetter understanding of these relationships and contribute to the development of effective therapeutic strategies.