The clinical diagnosis of frontotemporal dementia (FTD) can be challenging even to experienced clinicians. In the absence of a definitive clinical test, this diagnosis relies on behavioral criteria. Difficulty applying these criteria arise for four main reasons. First, FTD patients present with social and personality changes that defy the neuropsychological model of dementia. Second, FTD is not a single disorder but a spectrum of clinical syndromes with asymmetric and motor variants. Third, there may be qualitatively different symptoms during stages of FTD. Finally, pathologic and genetic variability contributes to the clinical variability. Future research should refine the clinical criteria for FTD using clinicopathological correlation in addition to working on the development of neurobiological markers.