A 7-year-old girl with the juvenile form of Huntington disease is described. She had personality changes, speech and gait disturbances, diffuse rigidity, dementia, and a well-documented family history of Huntington disease. Electroencephalography revealed bilateral epileptic foci; however, she had no seizures. Positron emission tomography using [18F]-2-fluoro-2-deoxy-D-glucose with an improved method for quantification of glucose metabolism in anatomically defined regions of interest demonstrated marked hypometabolism in the caudate nuclei and putamen, as is observed in adults with the disease. Glucose metabolism was also reduced in the posterior nuclei of the thalamus. Adults with Huntington disease have consistently demonstrated normal or increased rates of thalamic glucose metabolism. The findings suggest that brain metabolic alterations of Huntington disease in children differ from those in adults which is consistent with the postmortem pathologic differences previously recognized.