Many studies promote both diagnostic and prognostic roles for single photon emission computed tomography (SPECT) functional brain imaging in patients with cerebrovascular disease (CVD). SPECT allows in vivo non-invasive imaging and quantification of regional cerebral blood flow (rCBF). Main indications include stroke, transient cerebral ischaemia (TIA), intracranial haemorrhage and arteriovenous malformation (AVM). In all types of CVD, significant changes in brain perfusion occur. SPECT-rCBF imaging may be useful in defining stroke subtypes-pathogenesis and add critical information regarding patients therapy and clinical outcome. Moreover, calculation of regional cerebrovascular reserve (rCVR) at rest and during acetazolamide vasodilation reflects the brains autoregulatory process. In acute stroke, SPECT imaging is superior to CT and MRI in demonstrating cerebral ischaemia in the early hours of onset. Recent studies illustrate the prognostic value of early SPECT-rCBF imaging, in comparison with CT. Additionally, SPECT-rCBF studies are useful in identifying appropriate candidates for thrombolytic treatment and therapy monitoring. In patients with chronic symptoms and signs of CVD, but negative CT, a positive SPECT study indicates cerebral ischaemia correlated with arterial stenosis. Anatomic imaging contributes little to the diagnosis of TIA, while SPECT may be useful in determining the cause and in identifying patients at high risk for early stroke following a TIA. SPECT also has a clinical application in monitoring ischaemia associated with vasospasm following subarachnoid haemorrhage. Brain SPECT has an important role for steal documentation in patients with AVM, while the evaluation of CVR seems to be prognostic for postoperative outcome. In the future, more studies are needed, to answer focused clinical questions.