The major focus of our research has been on the design, development and evaluation of novel radiotracers based on small molecules for imaging specific molecular targets using positron emission tomography (PET). The imaging targets are usually enzymes, cell surface receptors or transporters that are strongly implicated in or markers of diseases. Fluorine-18, which has a half-life of about 110 min, is ideally suited for radiolabeling of small molecules, and permits PET imaging studies for up to 4 h after injection in vivo. Other radioisotopes of interest for PET radiotracer development include carbon-11 and iodine-124, the latter one has a longer half-life (4.2 days) and enables imaging for up to 1 week after injection of the labeled probe. Another major area of interest include the use of PET imaging for evaluation of novel therapeutics in preclinical models of diseases.