A 59-year-old man was admitted for further investigation of headache. Neurological examination revealed memory loss, disorientation, and bilateral intention tremor. Legionella pneumophila antigen was detected in the urine. Brain magnetic resonance diffusion-weighted images showed marked hyperintensity in the splenium of the corpus callosum without other abnormalities. Single photon emission CT with Tc-99m hexamethyl-propyleneamine oxime showed multi-focal hypoperfusion in the brain, involving mainly the cerebellum and frontal lobe. This is the first report demonstrating cerebellar and frontal lobe hypoperfusion without corresponding MRI abnormalities in a patient with central nervous system Legionnaires' disease.