Medical writers are increasingly likely to come across patient apps in their work, and we describe here the background and use of two apps for assessing patient-reported outcome (PRO). Systematic collection of PRO data via patient apps has been recently introduced in a large Danish university hospital. Experiences so far show that the approach can help staff to focus on the individual patient’s needs and can improve communication between patients and staff. Some patients have also been able to avoid unnecessary hospital visits. Effective clinical use of systematic PRO data requires the data to be easily accessed and visualised, and both patients and staff need to know that the data provided will make a meaningful contribution to health care.