In the past decade, the Norwegian government has emphasized user participation as an important goal in the care of mentally ill patients, through governmental strategic plans. At the same time, the governmental documents request normalization of psychiatric patients, including the re-socialization of psychiatric patients back into society outside the psychiatric hospital. Milieu therapy is a therapeutic tool to ensure user participation and re-socialization. Based on an ethnographic study in a long-term psychiatric ward in a psychiatric hospital, we identified how staff tried to implement user participation in their milieu-oriented therapy work. We have identified three major tensions and challenges in implementing user participation in milieu-therapeutic work. First, it is difficult to implement individual-based user participation and at the same time take collective house rules and codes of conduct into consideration. Second, user participation proved a difficulty when patients' viewpoints challenged staff judgements on proper conduct and goals for which patients might aim. Third, user participation becomes a challenge when trying to establish relationships based on equality when using milieu therapy in a biomedical hierarchical hospital structure. These tensions and challenges are seen in light of paradoxical political frames and demands on one side, and milieu therapy as a complex tradition anchored in different ideologies on the other.