Two cases of idiopathic restrictive cardiomyopathy in young age are reported. This rare kind of restrictive cardiomyopathy is characterized by the absence of specific histologic features of myocardial abnormalities. In both cases (aged 12 and 9 years at diagnosis), the clinical picture was characterized by severe and slowly progressive congestive heart failure. The electrocardiogram showed biventricular hypertrophy, right bundle branch block and pseudoinfarctional Q waves. Echocardiography revealed moderate pericardial effusion, biatrial enlargement, and normal or nearly normal biventricular dimensions and systolic function. Cardiac catheterization disclosed the typically restrictive filling pattern. Right ventricular endomyocardial biopsy demonstrated moderate interstitial fibrosis and cellular hypertrophy without any evidence of infiltrative or storage myocardial disease or endocardial pathology. One patient underwent cardiac transplantation, whereas in the other, transplantation was contraindicated because of longstanding pulmonary hypertension and liver cirrhosis. The knowledge of this rare entity may correctly orient the diagnostic process in children suspected of having restrictive myocardial disease. Heart, or even heart-lung, transplantation must be considered in cases with congestive heart failure before irreversible damage occurs in many organs.