A whole-body computed tomography system for single-photon emitters was evaluated from the standpoint of spatial resolution, sensitivity and thresholds for count densities regarding standard doses of currently used radiopharmaceuticals in patients. In air and tissue equivalents, spatial resolution was relatively constant throughout the field of view and attentuation correction algorithms returned uniformity of response to within 10%. In a phantom of the human abdomen 1.5-cm spherical cold lesions and 1-cm hot lesions could be resolved. Aspects of the partial-volume effect were observed and investigated. To detect 1.5 cm-cold lesions in an abdominal phantom, 5 million events were required.