The burden of dementia on health, social and economic well-being is enormous, whether viewed in terms of the 40 million people living with dementia (predicted 75 million by 2030) or the trillion-dollar cost per annum (predicted $2 trillion by 2030) [1]. In many parts of the world, mental health services provide the backbone to dementia diagnosis and management. The sections in this chapter focus on neurodegenerative disorders although several non-degenerative causes of dementia are considered alongside. Neurodegenerative disorders commonly present with changes in personality and behaviour that lead to referral for psychiatric assessment. Other common psychiatric disorders can mimic dementia, or complicate its management.