Molecular imaging tools, both equipment and agents, continue to improve and evolve, offering multimodality imaging with greater sensitivity and high-resolution of biological processes in real time. This review summarizes some of these recent developments in preclinical hardware, wetware and software, and their impact on drug development. The focus is on the advances in non-invasive small animal imaging such as positron emission tomography (PET), computed tomography (CT) and solid state detectors in single photon emission tomography (SPECT), which, when combined with labeled tracers serving as biomarkers and functional probes in vivo, are demonstrating the potential to accelerate our understanding of disease and help select drug candidates for development.