There is a pressing need for robust imaging markers to assist in the development of drugs for the treatment of atherosclerosis. Conventional imaging methods provide quantitative and morphological data but may be inadequate for assessing a new generation of therapies that modify plaque biology directly. Here, we compare the main imaging modalities used to image atherosclerosis in the clinical-trial setting, and assess their ability to predict clinical outcomes for a given sample size. We consider how emerging molecular and cellular imaging techniques could offer the possibility to quantify changes in biological function at the level of the plaque, even without gross structural change.