Infective endocarditis (IE) may lead to mycotic aortic root aneurysm formation. Herein is described the preoperative use of ECG-gated contrast-enhanced 256-slice cardiac computed tomography (CT) to optimize surgical planning by visualizing the location and extent of the mycotic aneurysm in two patients with complicated IE. In both cases, CT revealed a large aortic root mycotic aneurysm, accurately determined its location and extent, and also depicted the close relationship of the aneurysm to the major blood vessels. Intraoperative surgical findings corresponded to preoperative CT findings in both cases. Multislice CT is a valuable technique in patients with complicated IE that helps to optimize preoperative surgical planning.