Until today [F18]ethyl-diprenorphine-PET studies to evaluate opiate-receptor distribution in the brain have only been performed within a human model. Corresponding studies in rats to determine opiate-receptor distribution so far have been performed by using autoradiographic and immunohistochemical methods. Small animal PET promises to bridge this gap and now for the first time we are able to analyze F18-DPN-binding sites in rat-PET- experiments. In order to assess F18-DPN binding in rats dynamic scans were performed using small animal PET scanner microPET Focus 120 (Siemens). In human F18-DPN-PET studies the highest binding potentials are detected in the thalamus, the basal ganglia and the amygdala, strong signals are in the anterior cingulate cortex and the operculo-insular region and the lowest binding potential are in the sensory motor strip (Baumgärtner et al., 2006). High binding can be detected in the thalamus, the anterior cingulate cortex, the striatum and the amygdala. In the cortex the F18-DPN uptake is at an equally lower level whereas in the cerebellum no specific binding is visible. These results except for the cerebellum correspond to the recently performed F18-DPN-PET-studies in humans.