This prospective study was performed to determine whether juvenile or adult dogs with focal-onset epilepsy exhibit abnormal cerebral glucose uptake interictally and whether glucose uptake changes with age. 2-[18F]fluoro-2-deoxy-D-glucose (FDG) is widely used as a PET tracer in human epilepsy patients to help identify the seizure focus and was used in this study to examine six Lagotto Romagnolo dogs with juvenile epilepsy, two dogs with adult-onset epilepsy, and five controls. The dogs also had electroencephalography (EEG) performed. Visual analysis revealed areas of hypometabolism interictally in five out of six dogs with juvenile epilepsy. Changes in EEG occurred in three of these dogs. No hypometabolism was found in adult dogs.