To test the hypothesis that cerebral metabolism is altered in myotonic dystrophy (MyD), we investigated cerebral glucose kinetics and utilization in 11 adult patients with MyD and 14 healthy controls, using F-18-labeled 2-fluoro-2-deoxy-D-glucose (FDG) and dynamic positron emission tomography. Estimation of rate constants in MyD revealed a reduction of FDG delivery to the brain. Cortical glucose utilization rate was reduced by about 20% in MyD. These findings may be related to the presence of neurologic impairment in MyD and prompt further investigations on the metabolic and clinical features of brain dysfunction in this disease.