Abstract: Apoptosis is an important form of cell death and apoptosis imaging is of important clinical value for disease diagnosis and the evaluation of curative effects. One of the key issues of the molecular imaging technology is the development of specific molecular probes. At present, positron emission tomography (PET) is the most advanced molecular imaging technology, and in vivo noninvasive detection of cell apoptosis using the apoptotic PET tracers has become feasible in reality. Therefore, development of new small-molecule PET probes will be an important research field of molecular imaging. This review mainly describes the state of the art of smallmolecule PET probes and their applications to apoptosis imaging.