Background and Purpose-Little is known about the relevance of age related white matter lesions (WMLs) concerning outcome after first-ever territorial stroke. Based on an index patient, we hypothesized that age and pre-existent WMLs rather than infarct volume and topography determine outcome. Patients and Methods -Thirty-four consecutive patients with magnetic resonance diffusion-weighted imaging-proven isolated acute cerebellar infarction were prospectively entered on our stroke data registry. Patients with pre-existent neurological deficits, hemorrhagic, or malignant cerebellar infarction were excluded. Patients were stratified using Rankin and Barthel disability scales into groups: I complete recovery, II moderate, and III significant disability 14 days after stroke onset. Results-Initial neurological and functional scores were similar among all the groups with vertigo, nausea, unsteadiness, and limb ataxia being the most common. Infarct volume, vascular territories, and comorbidity did not predict clinical outcome. In contrast, presence and severity of supratentorial WMLs and age significantly determined outcome by functional tests. Conclusions-In patients with isolated cerebellar infarction functional outcome correlated with the coexistence of age-related WMLs rather than stroke volume and topography. This reflects the loss of compensatory network integrity as the equivalent of functional incapacity beyond local lesion disturbances. Background and Purpose-Little is known about the relevance of age related white matter lesions (WMLs) concerning outcome after first-ever territorial stroke. Based on an index patient, we hypothesized that age and pre-existent WMLs rather than infarct volume and topography determine Patients and Methods-Thirty-four consecutive patients with magnetic resonance diffusion-weighted imaging-proven isolated acute cerebellar infarction were prospectively entered on our stroke data registry. Patients with pre-existent neurological deficits, hemorrhagic, or malignant cerebellar infarction were excluded. Patients were stratified using Rankin and Barthel disability scales into groups: I complete recovery, II moderate, and III significant disability 14 days after stroke onset. Results-Initial neurological and functional scores were similar among all the groups with vertigo, nausea, unsteadiness, and limb ataxia being the most common. Infarct volume, vascular territories, and comorbidity did not predict clinical outcome. In contrast, presence and severity of supratentorial WMLs and age were significantly determined outcome by functional tests. Conclusions-In patients with isolated cerebellar infarction functional outcome correlated with the coexistence of age-related WMLs rather than stroke volume and topography. This reflects the loss of compensatory network integrity as the equivalent of functional incapacity beyond local lesion disturbances.