BACKGROUND: According to the involvement of oxidative stress in the pathogenesis of obesity, the plasma level of coenzyme q10 in the correlation relationship with lipid metabolism disorders and functional liver state is of interest to study.AIM: Substantiation of approaches to the correction of lipid metabolism disorders and non-alcoholic fatty liver disease in children with exogenous obesity based on the content of coenzyme Q10 and its relationship with lipid profile and liver enzymes.MATERIALS AND METHODS: The single-center cross-sectional study enlisted the control (n=32, -1.0≤BMI SD score ≤+2.0) and obese (n=40, BMI SD score>+2.0) groups of children with the mean age of 12 yr. In all children BMI, lipidogram, liver enzymes (ALT and AST), plasma coenzyme Q10 and liver ultrasound examination were assessed.RESULTS: Patients of both groups were comparable (p> 0.05) in age and gender. The level of coenzyme Q10 in the compared groups was comparable (p> 0.05) and did not differ in patients with different degrees of obesity. According to the results of the study of the lipid profile in the obese children, the level of HDL was lower, and the level of LDL was higher than that in control group. The highest value of HDL was obtained in the patients with the 1st degree of obesity and the highest level of triglycerides — in the patients with the 4th degree of obesity. The control group demonstrated moderate correlations between endogenous coenzyme Q10 and total cholesterol (r=0.474, p=0.009) which persists in patients with the first degree of obesity (r = 0.548, p = 0.035). There was no difference in AST in the study groups, however, the main group demonstrated elevated ALT and ALT/AST ratio (p <0.001). The highest ALT and ALT / AST ratio were observed in patients with greatest degree of obesity. Eighteen obese children (45%) had ALT / AST ratio ≥1 (in the control group –one patient (3%) (p <0.001), while fourteen patients showed liver enlargement and structure change according to ultrasound (80%). The control group demonstrated moderate correlations between endogenous coenzyme Q10 and total cholesterol (r=0.474, p=0.009) and between coenzyme Q10 and ALT / AST ratio (r=0.412, p=0.023) . In the obese group there was correlation between AI and ALT / AST (r = 0.436, p = 0.006) and in patients with the 1st degree of obesity — between also coenzyme Q10 and ALT (r = 0.875, p <0.001).CONCLUSION: The disturbances in adequate control of cholesterol by coenzyme Q10 in obese children possibly confirming the involvement of oxidative stress in the pathogenesis of dyslipidemia and non-alcoholic fatty liver disease can serve as indication to use coenzyme Q10 in order to correct these complications.