PET imaging enables, among others, noninvasive visualization of glucose metabolism using [18F]FDG. In focal epilepsy patients, the whole irritative zone is hypometabolic and called the functional deficit zone (FDZ). This is in contrast with the high physiological uptake in the surrounding healthy cortex. Interictal [18F]FDG PET can help to identify the seizure-onset zone both in temporal and extratemporal epilepsy. It plays a unique and important role in the presurgical workup for patients with drug-resistant epilepsy (DRE), more specifically in MRI-negative patients, when the MRI shows multiple lesions or when the MRI is discordant with other information such as the EEG or semiology. Moreover, it can provide prognostic information as surgical outcome is related to the extent of the hypometabolic zone beyond the seizure-onset zone.