We investigated whether obese children and adolescents have early echocardiographic signs of subclinical cardiac dysfunction and evaluated the respective influence of obesity per se versus parameters of carbohydrate and lipid metabolism that are frequently abnormal in obese subjects. The role of tissue Doppler imaging as a screening tool for these abnormalities was explored. Blood pressure and echocardiographic parameters, including tissue Doppler measurements of the septal mitral annulus were evaluated in 49 obese children and adolescents and 45 age and sex matched controls. The respective influence of obesity versus parameters of carbohydrate and lipid metabolism was examined with linear regression analysis. Obese subjects showed significantly larger left ventricular wall dimensions (posterior wall, septum, and left ventricular mass index) and signs of early diastolic filling abnormalities on conventional and tissue Doppler echocardiography compared with nonobese subjects. Multiple regression analysis showed that mainly BMI-SD scores and/or body surface area explained significant proportions of the variance of the early cardiac abnormalities. In conclusion, young, obese children and adolescents have significant changes in left ventricular wall dimensions and early diastolic filling compared with nonobese subjects. Obesity per se and not the parameters of carbohydrate and lipid metabolism predicted the early cardiac abnormalities.