INTRODUCTION : Evidence associates obesity with glomerular hyperfiltration. Concurrent inflammation, hypertension, dyslipidemia, and insulin resistance represent further established risks to renal health in both children and adults. Our aim was to investigate the relationship between childhood obesity and the risk of renal impairment. MATERIALS AND METHODS : A total of 114 obese but otherwise healthy children, who were investigated in 2013, were included in the study (mean age 11.5±3.6). Auxology was measured using standard procedures. The pubertal status was defined applying the Tanner scale. Blood and urine tests were performed after overnight fast. Kidney size was measured by standard abdominal ultrasound; kidney volume and estimated glomerular filtration rate were calculated. RESULTS : Microalbuminuria was detected in 8.5% of the children, and 40.2% of all patients were with high systolic blood pressure (BP). Close to half of the children (43.4%) showed insulin resistance (assessed by HOMA-IR) and 95.4% displayed hyperinsulinism. Kidney volume correlated with waist circumference (WC) (left r=0.636, p<0.001; right r=0.532, p<0.001), as well as with weight and elevated systolic BP. Children with hyperfiltration (9.6% of all) at this stage all had elevated total cholesterol and triglycerides. In further 14.3% of the children (all pubertal) the glomerular filtration rate was low, and they had significantly larger kidney volume (left p<0.001; right p=0.004), HOMA-IR (p=0.001), WC and BMI (p<0.001) compared to those with normal and hyperfiltration rate. CONCLUSION : To summarize, childhood obesity showed an association with established risk factors for renal toxicity. Whether kidney volume in obese children has an independent predictive value of future chronic kidney disease remains to be investigated.