In the presented study, the informative content of health data of a handwritten health diary was compared with health data submitted through a serious game. Physicians are able to derive a better and more complete health status of patients with higher informative content in health reports. The serious game was implemented in the project Interacct, in which patients submit health data through a mobile app on a daily basis to receive in-game rewards. The main hypothesis is, that the informative content of health data, which was submitted through a serious game, is higher than the informative content of hand written health diaries. Statistical results confirm this hypothesis significantly. This is especially important for young and adolescent cancer patients, where the results were even more conclusive than in the control group of students. Considering positive side effects of the serious game (such as high engagement, compliance and pleasure reporting health data through a serious game), the proposition of the authors is to conduct further studies and experiments regarding this topic.