Nuclear myocardial perfusion imaging is very effective in the evaluation of patients with suspicious acute coronary syndrome (ACS), for adequate diagnosis and treatment. There have been many clinical evidences to support the efficacy and cost-effectiveness. In addition, many authoritative guidelines support the utility of myocardial perfusion imaging in ACS with an appropriate diagnostic protocol. However, with the development of other cardiac imaging modalities, the choice of modality for the diagnosis of suspicious ACS now depends on the availability of each modality in each institute. Newly developed imaging technologies, especially including molecular imaging, are expected to have great potential not only for diagnosis but also for primary, secondary, and tertiary prevention of ACS. (Nucl Med Mol Imaging 2009;43(3):215-221)