We report findings on brain glucose metabolism and dopamine D2 receptors generated by positron emission tomography (PET) in a 67-year-old woman with right hemiparkinsonism-hemiatrophy syndrome (HP-HA). PET with [18F]-fluorodeoxy-glucose (FDG) showed marked glucose metabolism asymmetry. There were significant reductions in glucose uptake at the level of the basal ganglia and, to lesser extent, in the fronto-parietal cortex contralateral to the clinically involved side. These changes were different from those found in a patient with hemi-Parkinson's disease who was scanned under similar conditions. Because the patient with HP-HA had only minimal response to levodopa therapy, we evaluated post-synaptic dopaminergic structures using PET with [18F]-fluoroethylspiperone (FESP). No striatal binding asymmetry was found in FESP/PET, which suggests a sparing of striatal dopamine D2 receptors. The changes in FDG uptake which we found were in brain areas relevant to the clinical features of HP-HA syndrome. In addition, our study provides evidence that FDG/PET may help to differentiate HP-HA syndrome from hemi-Parkinson's disease. In most instances, since HP-HA is associated with a more benign clinical course than Parkinson's disease, this distinction is of clinical important.