Serious cardiovascular events frequently arise from rupture of vulnerable atherosclerotic plaques. Not infrequently, these plaques are clinically silent and suddenly cause acute complications such as myocardial infarction, which in a high percentage are fatal. Thus, identifying individual patients with vulnerable plaques at high risk for plaque rupture is a central challenge in clinical medicine. This review highlights noninvasive scintigraphic techniques, which use radiolabeled molecules to detect functional aspects in atherosclerotic plaques by visualizing their biological activity. One major principle is the molecular imaging of inflammation with radionuclide tracers, including detection of metabolic activity, chemotaxis, cell recruitment, and lipoprotein enrichment. Additional studies focus on visualization of apoptosis, angiogenesis, or proteolysis. A central feature of plaque vulnerability is its thrombogenicity. Therefore, detection of thrombogenic plaques is another promising principle of molecular imaging. If a reliable protocol to image vulnerable plaques, which are prone to rupture, can be established and introduced into clinical practice, the required measures such as atheroprotective medication or revascularization could be undertaken to prevent serious cardiovascular events.