The increasing number of people living into advanced old age raises profound questions about how society may achieve inter-generational equity, the nature of relationships between older people with lifelong mental health problems or more recently acquired age-related conditions and their carers, and the quality and availability of health and social care provision. This chapter primarily concerns dementia with some attention to functional mental illness in later life, most especially depression. It examines the policy framework, nature, prevalence and incidence, good care practice, service provision, and the role and contribution of professional social workers. It seeks to locate the discussion within the wider United Kingdom context but in particular draws on relevant Northern Ireland literature and research.