Dilated cardiomyopathy (DCM) is an important cause of chronic congestive cardiac failure in children. In patients with idiopathic DCM, endothelium vasomotor function is disturbed. There are many studies on the roles of nitric oxide (NO) and adrenomedullin (AM) in adult patients with DCM. However, to our knowledge, no studies have investigated the level of AM and NO in children with idiopathic DCM. We determined plasma and urinary AM and total nitrite concentrations in children with idiopathic DCM and investigated the correlation between these and other clinical and laboratory findings. Eleven patients with DCM, ranging in age from 5 month to 14 years, were compared to 10 healthy age- and sex-matched controls. Plasma (pmol/ml) and urinary (pmol/mg creatinine) AM levels were significantly lower than in the healthy controls (19.55 ± 2.36 vs 51.61 ± 7.22 and 28.29 ± 20.66 vs 68.87 ± 40.23, respectively; p < 0.001). Plasma and urinary AM levels were negatively correlated with ejection fraction (EF) and fractional shortening (FS). The plasma (µmol/L) and urinary nitrite levels (µmol/mg creatinine) were not different between patients and controls [50.90 ± 17.50 vs 53.40 ± 26.05 (p > 0.05) and 1.98 ± 1.24 vs 2.75 ± 1.68 (p > 0.05), respectively]. In our study, the first to analyze AM and nitrite levels in children with DCM, plasma and urinary AM levels were found to be decreased. A possible explanation for this reduction could be depletion of the viable myocyte population. However, this hypothesis must be clarified by further studies.