Obese children, without arterial hypertension, may be a unique clinical opportunity to evaluate the effect of obesity, per se, on ventricular repolarization, excluding the influence of possible comorbidities. The QTc dispersion (QTc-d), JTc dispersion (JTc-d), and transmural dispersion of repolarization (TDR) have been suggested to be electrocardiographic indexes reflecting the physiological variability of regional ventricular repolarization. The aim of our study is to define the effects of obesity on the ventricular repolarization in obese children who have no other clinically appreciable cause of heart disease. The study involved 70 subjects (48 male, 22 female), with a mean age (± standard deviation) of 13 ± 2 years. A total of 35 individuals were obese (Group A: 24 male, 11 female, mean body mass index [BMI] of 38.2 ± 5.8 kg/m(2) ), and 35 participants were healthy lean children (Group C: 24 male, 11 female, mean BMI of 22.3 ± 0.3 kg/m(2) ). Heart rate; QRS duration; maximum and minimum QT interval; and QTc-d, JTc-d, and TDR measurement were performed. Compared with the healthy control group, obese children presented increased values of the QTc-d, JTc-d, and TDR (31.1 ± 10.6 vs 46.2 ± 15.3 ms, P < 0.003; 29.8 ± 8.5 vs 40.1 ± 10.3 ms, P < 0.04; 83.2 ± 13.5 vs 100.7 ± 16.3 ms, P < 0.05). A statistically significant correlation was found between the values of QTc-d, insulin serum concentration (r = 0.46, P = 0.04), and homeostasis model assessment of insulin resistance (r = 0.34, P = 0.03). Our data suggest that obese nonhypertensive children have an increased ventricular repolarization heterogeneity in relation to controls. ©2010, The Authors. Journal compilation ©2010 Wiley Periodicals, Inc.