We investigated perceptions of identity in Alzheimer’s disease and behavioural-variant frontotemporal dementia. We asked family members of people with dementia to describe them before and after onset of the disease, comparing across type (Alzheimer’s disease versus behavioural-variant frontotemporal dementia) and time period. Family members’ perceptions of people with dementia changed over time. Compared with Alzheimer’s disease, behavioural-variant frontotemporal dementia was perceived to cause greater disruption to identity and more often associated with negative moral traits. We found a relationship between assessments of moral character and perceived self-continuity. Our data revealed different ways family members navigate stability and change in the identity of their loved ones with dementia.