Positron emission tomography (PET) scan with 18F-fluorodeoxyglucose (18F-FDG) was performed in a 14-year-old boy who had seizures suspected to have originated in mesial frontal lobe. The seizures occurred in clusters and were characterised by a change in the facial expression at seizure onset and complex motor manifestations consisting of kicking, swaying and screaming. Ictal EEG showed rhythmic alpha-waves in the left frontal area association with the ictus. Cerebral CT, MRI and SPECT revealed nothing of significance, but the PET brain scans showed frontal and parietal hypometabolism, which was most prominent in the left mesial frontal lobe. The present case suggests that FDG-PET scanning may be useful for the diagnosis of the mesial frontal epilepsy, when other imaging studies fail to show abnormalities.