Assessment of regional cerebral glucose metabolism by (18)F-2-fluoro-2-deoxy-D-glucose (FDG)-PET at resting state is a standard functional technique to assess cerebral function. Group studies identified significant regional metabolic impairment in asymptomatic individuals at increased risk for dementia. Substantial impairment of FDG uptake in temporoparietal association cortices emerges as a reliable predictor of rapid progression to dementia in mild cognitive impairment patients and could, therefore, serve as a biomarker for the diagnosis of prodromal Alzheimer's disease. Frontal and temporoparietal metabolic impairment is closely related to progression of disease in longitudinal studies, and multicenter studies suggest its utility as an outcome parameter to increase the efficiency of therapeutic trials.