Although Parkinson's disease with later dementia (PDD) and dementia with Lewy 
bodies (DLB) are pathologically characterized by the presence of intraneuronal 
Lewy inclusion bodies, amyloid deposition is also associated to varying degrees 
with both these disorders. Fibrillar amyloid load can now be quantitated in vivo 
with positron emission tomography (PET) using imaging biomarkers. Here the 
reported findings of 11C-PIB PET studies concerning the amyloid load associated 
with PD and its influence on dementia are reviewed. It is concluded that the 
presence of amyloid acts to accelerate the dementia process in Lewy body 
disorders, though has little influence on its nature. Anti-amyloid strategies 
could be a relevant approach for slowing dementia in a number of DLB and PDD 
cases.