The neurodegenerative disorder Alzheimer's disease (AD) is the most common form of dementia. It is characterized by progressive impairment of cognitive functions and behavior. To distinguish clinically AD from other forms of dementia is an ongoing challenge. In addition, although mild cognitive impairment (MCI) is recognized as a risk factor for dementia, it remains a challenge to predict on an individual level who will convert to become demented. Amyloid beta (Abeta) is one of the crucial pathological findings in AD. Recently, amyloid tracers for PET imaging have been developed successfully which may offer the unique possibility for measuring fibrillar Abeta load in the living brain. Therefore, in the near future positron emission tomography (PET) may become an important tool for in vivo amyloid imaging contributing to early (differential) diagnosis as well as evaluation of treatment response in AD. Moreover, Abeta may play a role in prediction the conversion of MCI to AD. In this paper we review the recent development of the molecular imaging technique PET and its different radiopharmaceuticals on the trail for imaging amyloid in AD and the conversion of MCI to AD.