Self-management has the potential to improve patient care and decrease healthcare costs. It is especially beneficial for patients suffering from chronic diseases that require continuous therapy and follow-up such as cystic fibrosis (CF). Mobile phones have become pervasive and, therefore, are perfectly suited for self-management. However, due to the large amount of time CF patients spend in their treatment, usability and usefulness are critical factors for the adoption of an assistive mobile application (App).In our work, we applied co-design in the development of high fidelity mockups for a CF Self-management App. The co-design was conducted as a series of workshops involving CF patients, theirs parents, as well as health professionals, from multiple countries in Europe. The results include design concepts and User Interface elements that conciliate the different perspectives between the stakeholders.This paper describes the co-design process, the resulting design and further considerations which emerged along the process.