Recent advances in multi-detector computed tomography(MDCT) have allowed us to assess coronary artery stenosis non -invasively. Moreover, recent MDCT studies revealed the differences in the plaque morphologies of culprit lesions in patients with ACS. Delayed-enhancement MRI is now recognized as the gold standard for identification of myocardial necrosis and myocardial viability compared with other imaging modalities. Cardiac MRI also allows simultaneous direct visualization of not only myocardial necrosis by delayed-enhancement MRI but also the area at risk by T2-weighted MRI. In this paper, we reviewed the role of MDCT and MRI in evaluating patients with acute coronary syndrome.