Reports on a study using Social Return on Investment (SROI) analysis to examine the impact and social value of peer support groups as an intervention for people with dementia. Three peer support groups in South London participated in the study. A separate SROI analysis was carried out for each individual group to find out what people valued about the groups and how they helped them. The report presents the outcomes for each group, the indicators for evidencing these outcomes and the quality and duration of outcomes experienced. It then provides detail on the methodology used to calculate the impact and the social return on investment. Overall, the study found that peer support groups provide positive outcomes for people with dementia, their carers and the volunteers who support the groups. The benefits of participating in peer support groups included: reduced isolation and loneliness; increased stimulation, including mental stimulation; and increased wellbeing. Carers experienced a reduction in carer stress, carer burden and reduction in the feeling of loneliness. Volunteers had an increased sense of wellbeing through their engagement with the group, improved knowledge of dementia and gained transferrable skills. Overall the study found that for every pound (£) of investment the social value created by the three groups evaluated ranged from £1.17 to £5.18.