The development of neuroimaging methods such as PET, has provided a new impulse to the study of the neural basis of cognitive functions, and has extended the field of inquiry from the analysis of the consequences of brain lesions to the functional investigations of brain activity, either in patients with selective neuropsychological deficits or in normal subjects engaged in cognitive tasks. Specific patterns of hypometabolism in neurological patients are associated with different profiles of memory deficits. [18F]FDG PET studies have confirmed the association of episodic memory with the structures of Papez's circuit and have shown correlations between short-term and semantic memory and the language areas. The identification of anatomo-functional networks involved in specific components of memory function in normal subjects is the aim of several PET activation studies. The results are in agreement with 'neural network' models of the neural basis of memory, as complex functions subserved by multiple interconnected cortical and subcortical structures.