Functional neuroimaging is playing an increasing role in psychiatry and has
moved from academic isolation into clinical practice. This review examines
the basis for the use of Single Photon Emission Computed Tomography the mo
st widely available functional modality, in the two important areas of deme
ntia and parkinsonism. Its contribution to the diagnosis and management of
patients is discussed and its likely impact in clinical trials indicated. A
s functional imaging moves closer to those most able to utilise its power i
ts impact in these and other areas of psychiatry and neurology will increas
e further.