Personality change is among criteria for the diagnosis of dementia. We examine first whether personality changes are related to severity of cognitive impairment in a linear or an inverted-U fashion in 1132 demented older people from the Canadian Study of Health and Aging (CSHA) and 921 unimpaired older people. The proportion with reported change was larger for all measures in the demented group than in the cognitively unimpaired group, and was more consistent with a linear increase in personality change with increasing cognitive impairment than with an inverted-U relationship, as seen in only one variable. In our second (longitudinal) study, we evaluate which aspects of personality change most in dementia; changes in mood and an exaggeration of existing traits were the variables most closely related to the development of dementia.