Current methods of neuroimaging have revolutionized the examination of patients with dementia. Clinical examination of these patients has identified cortical and subcortical patterns of dementia. Each of these patterns can be caused by various diseases. Mixed patterns also occur and also have several possible causes. Neuroimaging can be quite useful in confirming the clinical assessment of the pattern of dementia and in further refining the diagnosis. We review the pathophysiologic basis of and the clinical and neuroimaging findings in dementia, both cortical and subcortical. The roles of neuroimaging in diagnosis, prognostic assessment, and treatment evaluation are discussed.