Background: We have used intravascular ultrasound in an attempt to clarify the extent of vascular remodelling of the aortic arch after the repair of aortic coarctation by use of a subclavian flap. Methods: We investigated 13 patients with coarctation of the aorta, ranging in age from 1.4 to 43.0 months, with a mean of 20.8 months, who underwent aortoplasty by incorporation of a subclavian flap. The mean postoperative period was 19.6 months, with a range from 0.03 to 41.2 months. The luminal morphology of the aortic arch was evaluated by intravascular ultrasound at the time of post-operative catheterization. Results: We observed 3 cases longitudinally. Over the period of observation, we found three types of morphology of the aorta at the site of incorporation of the subclavian flap, namely a snowman shape with two inflection points, a pisiform shape with one inflection point, and a round shape without any points of inflection. There was a correlation between the cross-sectional shapes at the site of the subclavian flap in the postoperative period (p < 0.01). In each case, we measured the cross-sectional area at the site of subclavian flap, at the descending aorta, and at the distal aortic arch. The cross-sectional area, and the increment of the cross-sectional area at the site of subclavian flap, was larger. Conclusion: The shape of the lumen subsequent to repair of aortic coarctation changes progressively from a snowman, to a pisiform, and finally to a round shape. Greater growth of the subclavian flap compared to the native wall of the aorta was observed for at least the first 4 years after repair. This finding may improve our understanding of the remodelling process of the arterial trunks after surgical repair.