Imaging myocardial perfusion is essential in the management of acute coronary syndromes without ST elevation (ACS ST-) confirming the diagnosis of coronary lesions and quantifying the myocardial ischaemia, an important factor in the stratification of coronary risk. In ACS ST-, perfusion imaging allows evaluation of myocardial viability, diagnosis of residual ischaemia and also the detection of no-reflow phenomena after reperfusion procedures. Although myocardial scintigraphy is the reference method in clinical practice, it has many limitations such as its spatial resolution, its irradiation, its attenuation artefacts, and also the fact that it does not visualise the coronary arteries. This has led to the rapid development of two new non-invasive imaging techniques: cardiac MRI and ultrafast CT. The major advantage of MRI is the possibility of associating analysis of myocardial perfusion with that of cardiac muscle function by investigating right and left ventricular function at rest and during myocardial ischaemia stress tests and by analysis of myocardial viability. More recently, ultrafast CT has been clinically validated for coronary imaging. However, analysis of myocardial perfusion and ventricular function by CT scan is still only at the research stage.