© 2015, IPNA.Background: Hypertension (HT) is a major comorbidity of obesity that is associated with an increased risk of cardiovascular disease and higher mortality. The aim of our study was to evaluate cardiac function in obese hypertensive (OHT) and obese normotensive (ONT) pediatric patients and determine the effects of plasma nitric oxide (NOx) values on cardiac function, while demonstrating the role of plasma NOx in HT in obese pediatric patients. Methods: The study population consisted of 62 patients (27 boys, 35 girls), aged 13–18 years and 21 age-matched healthy controls. All subjects enrolled in the study underwent echocardiography (Echo) evaluation and ambulatory blood pressure monitoring for HT. Plasma NOx and biochemical values were studied in both patient groups separately. Results: Plasma NOx levels were found to be lower in the OHT group than in the ONT and control groups (p < 0.001) and to be negatively correlated with left ventricular mass index values (p < 0.05). Both the OHT and ONT groups had concentric hypertrophy of the heart. Conclusions: Plasma NOx plays an essential role in obesity-induced HT. Concentric hypertrophy of the left ventricle was found in both the OHT and ONT groups, indicating structural deformation of the heart.