This thesis addresses the process of user involvement in the development of information technology (IT) systems. The motive for this research is that there is still a need of more knowledge about how users can be involved in IT-development when the aim is to develop solutions that represent user needs. This is especially true when the IT-system is developed to attract users as private persons. One attempt to facilitate inclusion of private persons in IT development processes is a phenomenon called Living Lab. Living Labs is a human-centric research and development approach in which IT-systems are co-created, tested, and evaluated in the users' own private context. The Living Lab phenomena can be viewed in two ways, as an environment, and, as an approach and in this thesis, the perspective taken is Living Lab as an approach. Since the Living Lab phenomena is a rather new area there is a noticeable lack of theories and methods supporting its actions. Hence, the purpose of my research is to contribute to a successful use of Living Labs as a means for user involvement by answering the question: How can a Living Lab approach for user involvement that focus on user needs, be designed? To gain insights into the topic I have been involved in three development projects in which the aim was to develop IT solutions based on users' needs. The research method applied in this research is action research based on an interpretive stance; I have used different methods for data- collection, such as focus-group interviews, surveys, and work-shops. In short, the main lessons learned from this research relates to three overarching themes; User involvement, Grappling with user needs, and Living Labs. The first theme concern issues such as user characteristics, user roles, when and how users should be involved. The second theme is divided into two clusters, collecting user data, and generating and understanding user needs. Lessons related to collecting users data concern topics such as encouraging users, storytelling, understanding the social context and the users' situation. The lessons regarding generating and understanding user needs relates to users motivation, the importance of understanding different perspectives and different levels of user needs. The third theme relates to the key-principles of Living Lab approaches, and how these principles are handled, supported, and related to each other in user involvement processes that embrace a Living Lab approach. Based on the lessons learned about the three themes, a methodology called FormIT is formed. The aim of FormIT is to assist Living Lab activities in Living Lab environments, and the methodology is built on ten guidelines. These guidelines are Identify, Inform, Interact, Iterate, Involve, Influence, Inspire, Illuminate, Integrate, and Implement, and they support the design of a Living Lab way of user involvement processes and contribute to fulfil the key-principles of Living Labs. To conclude, this thesis contributes to the understanding of how data about user needs can be collected, generated, and understood through a Living Lab way of user involvement processes. This in turn, contributes to the development of future IT-systems based on user needs, which increases the probability for system acceptance among private persons.