A 48-year-old man experienced recurrent vertigo refractory to antiplatelet medications. Cerebral angiography showed occlusion of bilateral vertebral arteries with poor collateral circulation. PET using O2 gas showed reduced blood flow and metabolic rate of oxygen and elevated oxygen extraction fraction in bilateral cerebellar hemispheres. Subsequent F-FRP170 (1-(2-F-fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole) PET, which depicts hypoxic but viable tissue, revealed elevated tracer uptake in the same regions. After superficial temporal artery-posterior cerebral artery anastomosis, O-gas PET showed normalization of blood flow, metabolic rate of oxygen, and oxygen extraction fraction in bilateral cerebellar hemispheres. Abnormally elevated F-FRP-170 uptake was also resolved in those regions.