Prior to putting in place a percutaneous device, the assessment of the atrial septal defect anatomy is mandatory. The 3D transthoracic echocardiography is a non-invasive method bringing an imaging of the septal defect surface and its borders. Fifty-two patients ageing from 3 to 16 years old had a rotational 3D transthoracic echocardiography. Thirty-six (69%) were selected for a percutaneous closure (borders > 7 mm and a septal surface/atrial septal defect ratio > 2). Thirty-two of these selected patients (89%) benefited from the Amplatz prosthesis implantation with success. The maximal 3D diameter of the septal defect was 20 + 4 mm (14-30) compared to the mean size of prosthesis at 22 mm (18-30). Four of the 36 patients (aneurismal septum or a borderline septal surface/atrial septal defect ratio) were secondarily oriented to surgeons. Sixteen patients (31%) were selected directly to a surgical closure. The lack of borders or septal surface were confirmed by the surgical view. The 3D transthoracic echocardiography allows to define new criteria for the selection of patients prior to a percutaneous closure of atrial septal defects. This prospective study demonstrates that 9 out of 10 patients who had the 3D criteria had a percutaneous closure of the septal defect.