Several studies using positron emission tomography with 18F-fluorodeoxyglucose (18F-FDG) have revealed functional hypofrontality in schizophrenia. However, frontal hypometabolism is not consistently found and is not specific to schizophrenia. Basal ganglia glucose hypermetabolism related to neuroleptic treatment has been demonstrated. Methodological and clinical differences between studies are discussed in this paper.