PET has been a key component in the diagnostic armamentarium for evaluating neurodegenerative diseases such as Alzheimer's or Parkinson's disease. PET imaging has been used for the diagnosis of these disorders, for identification of their pathophysiology, and for following treatment of these disorders. Further, PET imaging has been extensively used for both research and clinical purposes. This chapter will review the current literature with regard to PET imaging and neurodegenerative disorders. This includes an evaluation of the most commonly used tracer (FDG) that measures cerebral metabolism, as well as neurotransmitter tracers, and tracers designed to reveal specific pathophysiological processes. With the ongoing development of a large variety of radiopharmaceuticals, PET imaging will continue to play a prominent role in research and clinical applications for neurodegenerative diseases.