Objectives– The study aimed to increase understanding of behavioural changes in frontotemporal dementia (FTD) and identify features that best differentiate FTD from Alzheimer's disease (AD) and cerebrovascular dementia (CvD). Methods– A semi-structured questionnaire was administered to carers of 30 FTD, 75 AD and 34 CvD patients. Results– Behavioural changes that strongly discriminated FTD from AD and to a lesser extent CvD were loss of emotions and insight, selfishness, disinhibition, personal neglect, gluttony and sweet food preference, wandering, motor and verbal stereotypies, loss of pain, echolalia and mutism. Irritability, hyposexuality and hypersomnia did not discriminate. Emotional, eating and stereotyped behaviours correctly classified 95% of patients using regression analysis. Conclusions– Behavioural characteristics accurately differentiate FTD from AD and CvD. The findings highlight the particular importance of affective change in FTD, and underline the role of the frontotemporal lobes in emotion.