Opsoclonus-myoclonus syndrome (OMS) is characterized by opsoclonus and arrhythmic myoclonic jerks predominantly involving the trunk, limbs, and head. We present two patients with OMS after respiratory tract infection who exhibited diffuse cerebral hypometabolism, particularly in the parieto-occipital cortex on 18F-fluorodeoxyglucose positron-emission tomography (F-FDG PET). This metabolic change might be a consequence rather than a direct cause of motor symptoms, which may be attributable to brainstem or cerebellar pathology.