The number of households with only elderly people and elderly couples who have no relatives is increasing, and how to decide the treatment for patients with dementia is an issue. Psychiatrists face these challenges as an attending physician in admission wards for dementia, a consultation liaison psychiatrist and a clinical ethics committee member. As it becomes difficult to understand and judge treatment due to the influence of dementia, decision-making support is required to decide the treatment according to the intentions of the person. When performing medical treatment based on consent, it is necessary to evaluate the medical consent capacity to confirm, and if there is a decline in this capacity, the multidisciplinary team and family members should estimate the intention of the patient and support decision making. If there is an advance directive or advanced care planning, it should be reflected in the decision. Moreover, attention should be paid to nonverbal reactions. A four-element model of "understanding", "appreciation", "reasoning", and "expressing choice" is generally used for medical consent assessment, and a semi-structured interview, such as MacArthur Competence Assessment Tool-Treatment (MacCAT-T), is used for detailed assessment. Consent capacity is affected by behavioral and psychological symptoms of dementia, such as depression and delirium, and patterns of cognitive decline. The capacity required also depends on the risks, complexity, and needs of the treatment. In decision―making support, communication skills and support for family members are also required, in which specialty as a psychiatrist is needed. The active involvement of psychiatrists in the treatment decision process is required to ensure that people with dementia retain their right to receive satisfactory medical care.
 Author's abstract