This review critically evaluates the current role of single photon emission tomography (SPET) imaging in the clinical management of patients with dementia. The classification of the dementias is discussed and the clinical and pathological features of the various dementing illnesses are described. Typical appearances on cerebral blood flow imaging are presented for each of the conditions, together with the findings on D2 dopaminergic receptor and muscarinic receptor imaging where this is relevant. The review concludes with a section on the clinical value of SPET imaging in dementia. SPET imaging can make a valuable contribution to the accurate clinical differentiation of dementia, providing findings are interpreted in the light of neurological evaluation and structural imaging. The possible future role of SPET imaging in the prediction and evaluation of response to future therapeutic agents is discussed.