Coronary angiography is increasingly performed with multi-detector row computed tomography (CT) in the clinical setting. Successful use of this method, however, depends on the radiologist's knowledge of its potential pitfalls and familiarity with methods for minimizing or avoiding them. To identify artifacts and other pitfalls that commonly degrade image quality and that could result in misinterpretation, contrast-enhanced coronary angiograms acquired with a multi-detector row CT scanner with four detector rows in 110 consecutive patients were analyzed. The problems identified were classified into four broad categories: (a) motion-related artifacts caused by cardiac, pulmonary, or other body motion; (b) beam-hardening effects caused by metallic implants, severe calcifications, or air bubbles in the pulmonary artery that obscured the underlying coronary vessel lumen; (c) structural artifacts produced by adjacent contrast material-filled structures and overlying vessels; and (d) artifacts that resulted from technical errors or limitations. The most frequently observed artifacts were those related to cardiac motion. The most effective methods for minimizing cardiac motion artifacts are (a) premedication with beta-blockers to maintain optimal heart rate during scanning and (b) optimal selection of the reconstruction window.