Background Governments in several countries attempt to strengthen user participation through instructing health‐care organizations to implement user participation initiatives. There is, however, little knowledge on the effect on patients' experience from comprehensive plans for enhancing user participation in whole health service organizations. Objective To investigate whether implementing a development plan intending to enhance user participation in a mental hospital had any effect on the patients' experience of user participation. Design, setting and participants A non‐randomized controlled study including patients in three mental hospitals in Central Norway, one intervention hospital and two control hospitals. Interventions A development plan intended to enhance user participation was implemented in the intervention hospital as a part of a larger reorganizational process. The plan included establishment of a patient education centre and a user office, purchase of user expertise, appointment of contact professionals for next of kin and improvement of the centre's information and the professional culture. Main outcome measures Perceptions of Care, Inpatient Treatment Alliance Scale and questions made for this study. Results A total of 1651 patients participated. Implementing a development plan in a mental hospital intending to enhance user participation had no significant effect on the patients' experience of user participation. Discussions and conclusions The lack of effect can be due to inappropriate initiatives or challenges in implementation processes. Further research should ensure that initiatives and implementation processes are appropriate to impact the patients' experience.