The subjects consisted of one patient with chronic type A and three patients with chronic type B aortic dissection, who underwent replacement of an aorta obliterating distal false lumen. After the repair, the formation of two layers was detected by direct scanning echocardiography within the false lumen even during heparinization. In all cases, postoperative computed tomography confirmed complete thrombosis of the false lumen. The formation of two layers was considered to be a reliable predictor of late thrombosis.