OBJECTIVE: Obesity or corpulence is a chronic endocrine-metabolic disease characterized by excessive accumulation of redundant energy in fat tissue. Obesity achieved an epidemic scope in adults, but also in children and adolescents and it represents an important public health problem, and presents the risk of developing chronic diseases, primarily cardiovascular disorders, diabetes and dyslipidemia. The objective of this study was to examine the connection between obesity and the concentration of interleukin 6 (IL-6) in the serum. MATERIALS AND METHODS: The study represents a cross-sectinal investigation of cases and controls by comparing the test group of 30 obese children and adolescents (13.1 ± 2.19) with a control group of 30 children with normal weight and with matched age (13.08 ± 2.24). The ratio of male and female subjects in both the control and the investigated group was 50:50. Body mass indeks (BMI), waist and hip circumferences, and systolic and diastolic blood pressure were measured in both groups. Standard metabolic parameters (fasting plasma glucose, total cholesterol, HDL, LDL, and triglycerides) were also measured by standardized methods. Fasting inzulin concentration and IL-6 were measured by the electrochemiluminescent immuno-method „ECLIA“. RESULTS: Anthropometric measures (BMI in kg / m², percentiles, z- values, waist and hips circumferences in centimetres, and arterial blood pressure in mmHg) of the investigated group and the adolescents, show a statistically significant difference when compared with children and adolescents of the control group (P < 0.001). The concentration of fasting insulin in mU / L, HDL and triglycerides in mmol / L show a statistically significant difference between groups (P < 0.001), while fasting glucose, total cholesterol and LDL in mmol / L did not show statistically significant differences (P = 0.814, P = 0.615, P = 0.739). Serum concentration of IL-6 of the investigated group (2.21 ± 0.81 pg / mL) and the control group (1.56 ± 0.53 pg / mL) shows a statistically significant difference between groups (P = 0.039). CONCLUSIONS: The study confirms a higher concentration of IL-6 in the investigated group of obese children. The results show that the immunochemical method for analysing serum samples of obese children is sufficiently precise and specific. Since the pathogenesis of obesity is complex, it is necessary to conduct further studies that would include larger number of subjects both in the investigated and the control group.