The self-regulatory model proposes that illness representations influence adjustment and coping in chronic conditions. Better understanding of the illness representations held by people with dementia could help with targeting information and support so as to optimize adjustment and coping. In this mixed-methods study of illness representations among people with mild to moderate Alzheimer’s, vascular, or mixed dementia we aimed to clarify the nature of the representations held, to determine whether specific profiles can be identified based on perceptions of the identity and cause of the condition, and to examine associations between these profiles and other participant characteristics. Data were collected in the second wave of the Memory Impairment and Dementia Awareness Study (MIDAS). Sixty-four people with dementia, who had been told their diagnosis at a memory clinic, completed interviews and responded to questionnaires. In each case a carer was also interviewed. Cluster analysis based on responses about identity and cause identified three profiles. ‘Illness’ cluster participants saw themselves as living with an illness and used diagnostic labels, ‘ageing’ cluster participants did not use diagnostic labels and viewed their difficulties as related to ageing, and ‘no problem’ cluster participants considered that they did not have any difficulties. ‘Illness’ cluster participants had better cognition and better awareness, but lower mood, and perceived more practical consequences, than ‘ageing’ cluster participants. Holding an ‘illness’ model may not be advantageous. Rather than encouraging adoption of such a model, it may be preferable to target information and select interventions in line with the person’s representation profile.