With the advent of helical CT, the capability of noninvasive imaging of the thoracic aorta has been enhanced considerably. In this article, we describe the potential of helical CT using dual-slice technology to evaluate thoracic aortic diseases such as dissection, aneurysm, trauma, infection, inflammation, thromboembolic disease, and postoperative complications. Technical considerations for optimal CT imaging as well as limitations of helical CT are highlighted.