Objective: This study aimes to evaluate the echocardiographic changes before and after atrial septal defect closure in children under 15 years old. Methods: 31 patients (20F/11M) of atrial septal defect ASD ostium secundum with an age average of 9,19 + or - 4,58 (2-15 years) and the mean ASD size of 20,71 + or - 7,81 mm, mean Qp/Qs of 3,04 + or - 1,37 had indications for ASD closure (slow physical development and/or right ventricular [RV] enlargement by echocardiography). Follow-up at 1 week, 1 month, 3 month, 6 month after ASD closure. Results: All of the children had improvement of their weight. The dimensions of right ventricle, pulmonary artery diameter, pulmonary pressure and Qp/Qs decreased significantly (p0,0001) and normalised 6 month after ASD closure. No trivial shunts. Condusions: atrial septal defect (ASD) dosure in children S 15years improved significantly cardiac morphologic, hemodynamic parameters that why ASD dosure in children should be done as soon as possible in order to improve physical development of children.