Background: In the U.K. about 141,460 people with dementia (PWD) live alone. They are at risk of social isolation and inadequate social and medical supervision. The aims of this study were to identify the needs of PWD living alone and to compare the needs of PWD living alone versus those living with others. It was predicted that PWD living alone would have significantly more unmet needs than those living with others.; Methods: 152 PWD were interviewed about their cognitive status and quality of life (QoL); and 128 informal carers were interviewed about the PWD's QoL, social networks, behavioral and psychological symptoms (BPSD), functional status, and services used. For 24 PWD no carer was available. Carers were also interviewed about their own symptoms of depression, anxiety, burden, and satisfaction. Researchers rated PWD's needs. One-third of the PWD (50) were living alone.; Results: PWD living alone had significantly more unmet needs (M = 3.9, s.d. 3.1) than those living with others (M = 2.0, s.d. 2.0) (U = 1578, p < 0.01) particularly in the areas of looking after home (χ2 = 17.23, p < 0.001), food (χ2 = 13.91, p < 0.002), self-care (χ2 = 10.23, p < 0.002) and accidental self-harm (χ2 = 16.51, p < 0.001). The most frequent unmet needs were daytime activities (27, 54.0%), company (26, 52.0%), psychological distress (22, 44.0%), eyesight/hearing (16, 32.0%), and accidental self-harm (16, 32.0%). Conclusion: PWD living alone are a vulnerable group who are at increased risk for unmet social, environmental, psychological and medical needs. This study illustrates the need to identify these individuals and to make provisions among social service agencies to monitor their well-being regularly and provide a higher level of support when needs are identified.