This project examines how adult psychiatric patients perceive and experience questionnaires used to assess shared decision-making in relation to medication treatment. While the broader study links patient-reported involvement in decision-making to treatment adherence using survey and register data, this subproject focuses on a qualitative evaluation of the questionnaires themselves. We will conduct semistructured interviews with patients via Zoom, with audio recorded using a mobile phone for secure and flexible data capture. The interviews will explore how questionnaire items are understood and interpreted, their perceived relevance, emotional impact, and whether they adequately reflect patients’ experiences of involvement in medication-related decisions. Data collection will take place shortly after questionnaire completion to ensure that reflections are grounded in recent experience. Interview data will be analyzed thematically to identify strengths and limitations of the questionnaires from a patient perspective, including potential misunderstandings, response burden, and contextual factors influencing responses. By incorporating patient perspectives, this study aims to improve the validity, acceptability, and usability of patient-reported measures of shared decision-making in adult psychiatric care, supporting more patient-centered and reliable data collection in future research.