Alzheimer's disease (AD) is an example of cortical dementia, where most of the pathological changes lie in cortical association areas and the predominant clinical features are symptomatic of cortical dysfunction. The differential diagnosis of AD is complex and is usually made in two stages: diagnosis of the dementia syndrome and diagnosis of the underlying etiology. Each of these stages is complicated by the existence of conditions that mimic dementia in presentation and by the risk of inappropriately diagnosing AD where other conditions are responsible for the dementia state. Despite the fact that the concept of dementia, in terms of a decline in cognitive function and behavioral change, has existed for many years, there is still a general lack of agreement about the components of the syndrome. This article reviews the issues surrounding the differential diagnosis of the dementia syndrome and explores the points of differentiation between AD and some similar etiologies encountered when making a differential diagnosis.