We present a method for developing multi-device services which allows for the creation of services that are adapted to a wide range of devices. Users have a wide selection of electronic services at their disposal such as shopping, banking, gaming, and messaging. They interact with these services using the computing devices they prefer or have access to, which can vary between situations. In some cases, the services that they want to use func-tions with the device they have access to, and sometimes it does not. Thus, in order for users to experience their full benefits, electronic services will need to become more flexible. They will need to be multi-device services, i.e. be accessible from different devices. We show that multi-device services are often used in different ways on different devices due to variations in device capabilities, purpose of use, context of use, and usability. This suggests that multi-device services not only need to be accessible from more than one device, they also need to be able to present functionality and user interfaces that suit various devices and situations of use. The key problem addressed in this work is that there are too many device-service combinations for developing a service version for each device. In-stead, there is a need for new methods for developing multi-device services which allows the creation of services that are adapted to various devices and situations. The challenge of designing and implementing multi-device services has been addressed in two ways in the present work: through the study of real-life use of multi-device services and through the creation of a development method for multi-device services. Studying use of multi-device services has gener-ated knowledge about how to design such services which give users the best worth. The work with development methods has resulted in a design model building on the separation of form and content, thus making it possible to create different presentations to the same content. In concrete terms, the work has resulted in design guidelines for multi-device services and a system prototype based on the principles of separation between form and content, and presentation control.