Eldergames is a EU funded project to develop games using advanced visualisation and interaction interfaces to improve the cognitive, functional and social skills of older users. The project merges two major areas to which technology for the elderly people is applied, health and social engagement. Its platform will allow to improve the users’ cognitive skill and individual well-being by playing on a mixed reality platform; on the other hand, it will offer the unusual experience of communicating with people located on other countries without the need to share the same language. After introducing the field of gerontology and the project, the paper describes the main cognitive abilities that change with aging (perception, attention, memory, and other more specific processes such as decision making), and that have to be taken into account while designing a technology for the elderly people. Some guidelines that are specifically meant to ensure usability of these products are listed in the conclusions.