We have used single photon emission computed tomography to study cerebral blood flow (CBF), CBF reactivity to acetazolamide, and cerebral blood volume (CBV) in 15 subjects presenting widespread leukoaraiosis, with the aim of answering the question if chronic ischaemia or hypo metabolism is associated with leukoaraiosis. We compared these subjects to 9 controls presenting no leukoaraiosis but with similarly distributed factors for leukoaraiosis. The subjects with leukoaraiosis showed a low regional (r)CBF in their white matter, while CBV and CBF reactivity to acetazolamide were not significantly affected. rCBF, rCBV and rCBF reactivity to acetazolamide did not differ between the cortex of patients and controls. Our results suggest that the low white matter CBF of the patients with leukoaraiosis was related mainly to hypometabolism and not to oligaemia. The capacity of the cerebral vessels to vasodilate does not appear to be affected by leukoaraiosis.