This study was conducted to assess the use of serum cardiac troponin T (cTnT) level as a noninvasive indicator to diagnose acute myocarditis in children. Noninvasive conventional methods often fail to diagnose myocarditis, A median cTnT level of 0.088 ng/ml (0.04-3.11) was reported in pediatric patients with acute myocarditis in our previous study. Hence, we attempted to determine the cutfoff level of cTnT to diagnose acute myocarditis in children. Pediatric patients with clinically suspected myocarditis or dilated cardiomyopathy (DCM) and a control group were recruited. History, physical examination, elctrocardiogram, chest roentgenogram, echocardiogram, cTnT level, and/or endomyocardial biopsy and clinical course were studied. The gold standard to diagnose acute myocarditis was endomyocardial biopsy proved according to the Dallas criteria and/or recovery from cardiovascular problems within 6 months of follow-up. Forty-three patients were admitted due to cardiovascular problems from primary myocardial dysfunction. Twenty-four patients were diagnosed as acute myocarditis (group 1), 19 were idiopathic chronic DCM (group 2), and 21 patients had moderate to large ventricular septal defect and congestive heart failure (group 3). Median cTnT level was statistically higher in (group 1) compared to groups 2 and 3. Ejection fraction (EF) and left ventricular end diastolic dimension (LVEDd) z score of acute myocarditis were 38.5% (range, 21-67) and 1.3 (range, -0.8-3.0), respectively, which were significantly better than DCM [28.0% (range, 17-45) and 6.0 (range, 2.0-10.0)]. The cutoff point of cTnT level to diagnose acute myocarditis was 0.052 ng/ml (sensitivity, 71%; specificity, 86%). cTnT level, EF, and LVEDd z score did not predict short-term outcomes of patients. In acute myocarditis, cTnT level and EF were significantly higher and LVEDd z score was significantly lower than in DCM. However, the three parameters had no significant effect on outcomes of the patients. Our data show that cardiac a cTnT level of 0.052 ng/ml is an appropriate cutoff point for the diagnosis of acute myocarditis.