We reviewed records of patients seen in a tertiary Neurobehavior Clinic to identify those who had community-acquired PET scans as part of their dementia diagnostic evaluation with the goal of assessing factors influencing diagnostic accuracy. We compared outside radiologist PET diagnoses to our consensus clinical diagnosis and collected data regarding clinical variables, ordering reasons, and specialties of interpreting and ordering physicians. Among 1,580 total patients seen in our clinic, 46 met our inclusion criteria. There was disagreement between outside diagnosis based on PET and our consensus diagnosis in 65% (n = 30) of patients. Community-acquired PET scans may have lower diagnostic value in dementia evaluation than suggested by prior research and may be associated with significant risks including misdiagnosis with an incurable neurodegenerative disease.