Introduction: During the winter of 2009, some patients infected with Influenza virus H1N1 presented a severe disease. Some isolated reports of myocarditis were described. Objective: To describe severe cases of H1N1 with myocardial involvement. Patients and Methods: Chart review of children between 0-15 y.o. diagnosed as presenting Influenza A H1N1 through Polimerase Chain Reaction, who were admitted to the PICU at Hospital Roberto del Río and Clínica Dávila between June and July of 2009. Myocardial involvement was considered positive if the clinical picture showed such signs, and/or there was an altered echocardiogram. Results: Twenty one patients were hospitalized with the diagnosis of severe Infection by Influenza A H1N1 (+), of which 8 patients (38%) presented myocardial involvement. All required mechanical ventilation. Echocardiogram performed in the first 24 hours post admission showed shortening of the left ventricle on average 21,8%, with a range of 19 to 38%. In 7 patients (87.5%) a systodyastolic dysfunction was shown. Myocardial involvement lasted from 2 to 10 days (median 4). One patient died. Conclusions: Involvement of myocardium is frequent in this series. It must be sought to treat it adequately.