The European Health Data Space (EHDS) is a new EU regulatory framework for the use and re-use of health data with implications for citizens across the Union. It empowers citizens in primary uses of data, such as accessing electronic health records, but their role in secondary uses remains less clearly defined. The study interviewed health data experts in 23 European countries to understand views on citizen engagement in data reuse. Experts emphasized the importance of wider citizen involvement to raise awareness of EHDS and incorporate their perspectives into governance structures. They see a clear demonstration of the value of EHDS as key to strengthening public trust and acceptance. The study provides member states with knowledge for developing strategies for citizen involvement in the secondary use of data in EHDS. It emphasizes an easily accessible opt-out mechanism with clear communication to prevent misinformation, highlight the benefits of data sharing and take into account institutional trust and country contexts.