We report a new case of giant cell angiitis of the central nervous system associated with cerebral amyloid angiopathy (GA/CAA). A 67-year-old woman was hospitalized with a history of headaches and lapses of consciousness. After improvement with corticosteroidtherpay, treatment was stopped. She relapsed and died 33 days after first admission. Pathological examination showed unusual extension of GA/CAA lesions, in the superficial and deep layer of the cerebral cortex, and in the cerebellum. Simultaneous occurrence of GA and CAA is rare. Histopathologic findings and immunological pathogenesis of the process are discussed: 1) arguments over pre-existence of CAA, responsible for GA; 2) primitive inflammatory process inducing amyloid deposits; 3) GA/CAA may represent an association of histological lesions related to 2 different types of disease: i) neurodegenerative disease with specific lesions (such as presence of diffuse senile plaques and neurofibrillary tangles) inducing inflammatory reaction ii) inflammatory disease, with few or no degenerative lesions, responding to immunotherapy.