Predicting the occurrence of acute coronary syndrome (ACS) is a major clinical challenge for cardiologists. Multi-slice computed tomography (CT) has enabled easy detection and assessment of atherosclerotic coronary plaque, and therefore has considerable potential in the prevention of ACS. The recent development of 64-slice cardiac CT enables detailed information on both plaque properties and characteristics to be obtained with excellent diagnostic accuracy. Cardiac CT therefore has great potential for detecting the unstable plaques that are prone to result in ACS. (Circ J 2011; 75: 2013-2018)