Cerebral blood flow and metabolism were evaluated in an adult with symptomatic intractable epilepsy and Sturge-Weber syndrome (SWS) manifesting as angiomas in the left cerebral hemisphere. 99mTc-ethylcysteinate dimer single photon emission computed tomography detected reduced blood flow in the entire left cerebral hemisphere, and [18F]fluorodeoxyglucose positron emission tomography (PET) showed decreased glucose metabolism in the left cerebral hemisphere. These findings indicated hypofunction of the left cerebral hemisphere, which caused the right hemiparesis. 11C-methionine (11C-Met) PET revealed high 11C-Met accumulation in the angiomas in the left cerebral hemisphere. Immunostaining for glial fibrillary acidic protein showed positive reaction in the lesions. Gliosis is a likely mechanism for the 11C-Met accumulation, which is possibly associated with progressive calcification in the angiomas and retarded growth of patients with SWS occurring over many years.