A major advancement in the field of medicine has been the timely advent of amyloid imaging, which has allowed critical evaluation of the complex relationship between amyloid β peptide (Aβ) aggregation and Alzheimer's disease in vivo. Most importantly, amyloid imaging has the potential to detect Aβ in mildly affected as well as asymptomatic individuals, when the therapeutic window of opportunity might still be open to pharmacological intervention. It also shows significant promise in differential diagnosis of mild cognitive impairment or atypical dementias. Amyloid imaging studies support a model in which amyloid aggregation is considered an early event on the path of dementia, beginning insidiously in cognitively healthy individuals being accompanied by subtle cognitive, functional and structural brain alterations suggestive of incipient AD. As individuals progress to dementia, clinical decline and neurodegeneration accelerate and might proceed independently of amyloid accumulation. In this review we focus on amyloid imaging with particular emphasis on [11C]PIB in AD, mild cognitive impairment and other dementias, and discuss the advances made in this perplexing field.