In the UK, the number of people with dementia is increasing along with life expectancy - over half of the £23bn annual cost of dementia is due to informal care time. Therefore, there is an economic argument for identifying clinically-effective and cost-effective ways to maintain and improve carer quality of life (QoL). This thesis explores the suitability of a capability based instrument, the ICECAP-O, for measuring QoL in informal carers of people with dementia. Methods: Systematic reviews, qualitative interviews, survey data and clinical trial data were used.