OBJECTIVES: Studies evaluating computer-aided routinely assessment of patient reported outcomes (PRO) suggest important benefits for physicians, patients and their treatment. This project's aim was developing a flag system for computerized detection of cancer patients with additional treatment needs. METHODS: The detection system is part of the “Computer based Health Evaluation System (CHES)”, a software for the computerized collection, processing and presentation of PRO data. The flag system helps identify cancer patients with conspicuous subscale patterns. This includes cut-off values (patients marked with orange or red buttons) and significant changes over time (yellow deltas). The testing data set was derived from a longitudinal study on QOL (assessed using the EORTC QLQ-C30) in chemotherapy patients at an oncological outpatient unit. Several criteria of “relevant” changes were compared regarding the prevalence of such changes in the study population and their statistical significance on an individual patient level. RESULTS: QOL data of 167 cancer patients were analysed (on average 5.3 assessments per patient). The 75th and 90th percentile showed to be useful cut-off values. Recommended thresholds of relevant QOL changes appear to be unduly low when considering changes in the individual patient. Based on empirical data we suggest a modified criterion of relevant change for the EORTC QLQ-C30 which appears clinically and statistically more meaningful. CONCLUSIONS: The developed flag system enables physicians to detect patient reported health deficits (e.g. fatigue) at one glance. However, more research involving various diagnostic groups is needed for a more profound empirical basis for developing refined criteria.