The authors compared prospective (n = 20) and retrospective (n = 20) electrocardiography (ECG)-assisted multi-detector row computed tomography (CT) with non-ECG-assisted multi-detector row CT (n = 20) of the thoracic aorta with regard to reduction of motion-related artifacts. Image quality was rated for transverse source and sagittal oblique images of the thoracic aorta, including the aortic valve. ECG-assisted multi-detector row CT compared with non-ECG-assisted multi-detector row CT showed a significant reduction in motion artifacts for the entire thoracic aorta.