One of the most challenging and potentially rewarding research applications of PET is imaging of the mouse brain. Although very high spatial resolution is required (< ∼ 1 mm), there is a much wider variety of transgenic models in mouse compared to the rat. The solid state material CdZnTe (CZT) has long held promise for high resolution PET. Compared to scintillators, its limitations in time resolution and sensitivity can in some ways be compensated by its extremely high spatial and energy resolution, its compact geometry, and by sophisticated data processing techniques. Using such techniques, a time resolution of ∼10 ns has been demonstrated for ∼1 cm thick CZT pixel detectors, and this may be sufficient for mouse studies. The depth-of-interaction capability and high energy resolution can improve sensitivity by allowing detectors to be placed very close to the subject and by enabling both reconstruction of detector-scattered events and rejection of object-scattered events. A full-ring prototype scanner has been designed to demonstrate feasibility of the concept, consisting of 6 CZT pixel detectors in a novel geometry. The design of the detector, front-end electronics components, and data acquisition are presented, along with performance characterization of the custom-manufactured CZT detectors.