This paper discusses the incorporation of assistive technologies into dementia care. Dementia care is difficult because it heavily depends on the context, for example, the caregivers involved in dementia care, the persons being cared for, and the devices employed. In the attempt to develop and apply assistive technologies to the real world, the context dependence of dementia care has not been extensively studied. This paper describes two case studies involving a camera system and an RFID slipper system to focus on the issues involved in the development and deployment of assistive technologies. It is important to consider two factors: reduction of system operation costs for caregivers in dealing with multiple tasks and adjustment of the system on the basis of the personal histories of persons with dementia. To prevent unnecessary behavioral changes in persons with dementia and their caregivers, engineers must specifically consider the abovementioned factors during the installation of assistive technologies in the real world.