CMD is the most common cardiomyopathy in children. Epidemiological data show that it is more common in infants, males and blacks. Looking for parental consanguinity or an affected family member is an important part of the anamnesis. Clinically, it generally presents as acute heart failure. Cardiac ultrasound confirms the diagnosis, showing a dilated heart that contracts poorly. Cardiac MRI is a powerful tool for orienting etiological research and predicting prognosis. CMD in children is classified into primary and secondary CMD. Primary CMDs are hereditary or metabolic in origin, whereas secondary CMDs may be the consequence of a left-sided obstruction, a long-standing left-right shunt, a rhythm or conduction disorder, a birth defect of the coronary arteries, or viral or autoimmune myocarditis. Management is based primarily on treatment of cardiac decompensation. In the case of primary CMD, and in the absence of recovery, heart transplantation is the only hope of life.