The process of drug and molecular imaging development is strongly influenced by the revolution of non-invasive imaging techniques. Small animal positron emission tomography (PET) has the potential to accelerate and streamline drug and molecular imaging discovery and development by preselection of suitable candidate molecules. Due to its significantly improved spatial resolution and its quantitative nature, compared to other techniques small animal PET can be employed to bridge the in vitro, through to preclinical and clinical imaging in humans.