A 25-year-old woman with intractable seizures underwent FDG PET/MRI for seizure focus localization. MRI demonstrated bilateral carpetlike nodular subependymal gray matter and asymmetrical focal dilatation in the right temporal horn. PET/MRI showed increased FDG within subependymal gray matter with significant hypometabolism in right anterior temporal lobe. EEG and ictal semiology confirmed the right temporal seizure origin. This case highlights the importance of identification of gray matter heterotopia on FDG PET/MRI.