Systematic research is needed to evaluate the exact role of pathological factors in the determination of the extension of the hypometabolic area in partial epileptic patients. Together with structural damage, previous seizures, deafferentation and inhibitory mechanisms may contribute to the functional disorders. Benzodiazepine receptor studies showed that the density and binding ability of these receptors decreased in the area of epileptic functional disorder. Circumscribed hypermetabolism may appear during epileptic seizures or even more electrical discharges. The authors' PET studies aimed at presurgical evaluation showed that bilateral temporal hypometabolism occurred more frequently with right-sided seizure start. FDG-PET supported the localization of the pacemaker area both in temporal lobe epilepsies and in extratemporal epilepsies. This method proved instrumental in delineating the extension of the background pathology, too. The authors also demonstrated the strength of PET brain activation in mapping the hemispheric distribution of speech functions required in the planning of surgical interventions. The role of hippocampal sclerosis in temporal lobe hypometabolism was investigated and a short account is given of the observations relating to the relationship of hypermetabolism due to subclinical epileptic discharges and cognitive deficit symptoms.