The development of quantitative in vivo measures for differentiating Alzheimer's disease (AD), from other forms of dementia, such as Frontotemporal dementia (FTD), is of great clinical significance. Correct differential diagnoses of dementias are increasingly important as new treatments become available. AD neuropathology is characterized by the presence extracellular amyloid-β peptide fibrils and intracellular neurofibrillary tangles. While neurofibrillary changes may be present in other forms of dementia, for example frontotemporal dementia with parkinsonism (FTDP), Aβ accumulation appears to be specific to AD. PET imaging with Pittsburgh compound-B (PIB) has been shown to be effective in identifying amyloid deposition in mild cognitive impairment (Klunk et al., SFN 2003) and Alzheimer’s patients (Klunk et al., 2004). In this study, we compare the uptake of PIB in AD, FTD, and healthy older individuals. Patients were recruited and evaluated at the USCF memory and aging center, and the AD diagnosis was ba...