We report 2 cases of suspected low-grade glioma with positive 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET scan, and histological diagnosis of brain inflammation corresponding to an acute disseminated encephalomyelitis (ADEM) and to a neurosarcoidosis. It has been shown that this amino-acid PET radiotracer serves to evaluate tumoral proliferation related to the metabolism of L-amino-acid transporters, and that inflammation may also contribute to the tumoral uptake. This report suggests it may serve to study brain inflammation.