Non compaction of the ventricular myocardium is a rare and severe myocardiopathy with numerous trabeculations and deep intertrabecular recesses directly connected with the ventricular cavity. Many complications may occur: heart failure, arrythmia, thrombotic events. However, phenotypic and genotypic presentations vary. Non compaction affects infants in almost half of the cases. A pediatric national cohort study (directed by the filiale de cardiologie pédiatrique de la société française de cardiologie) should allow to analyse the clinical and epidemiological characteristics of the patients as well as to accurate both non compaction's diagnosis and prognosis. Inclusion criteria of this retrospective multicenter study were: age lesser than 18, echographic and/or histologic criteria of non compaction, no congenital heart disease such as pulmonary atresia. This population included 38 patients: 21 were asymptomatic at diagnosis. Ten familial forms were detected. The ECG was abnormal in 77% of the cases, the chest-X ray in 80%. Echocardiography remains the usual technique for diagnosis. However, previously reported quantitative criteria are not easy to use in a retrospective study. Treatment was symptomatic as the etiology of non compaction is unknown. The prognosis is severe: 31.5% of the patients died or had a cardiac transplantation. Only 30% of the patients were free of cardiac events for a 2-year period. Inclusion of new patients must go on to set up a prospective study and biomolecular analysis in informative families.