Systematic quality improvement (QI) interventions are increasingly used to change complex health care systems. Results of randomized clinical trials can provide quantitative evidence whether QI interventions were effective but they do not teach us why and how QI was (not) achieved. Qualitative research methods can answer these questions but typically involve only a small group of respondents against high resources. Concept mapping methodology overcomes these drawbacks by integrating results from qualitative group sessions with multivariate statistical analysis to represent ideas of diverse stakeholders visually on maps in an efficient way. This paper aims to describe how to use concept mapping to qualitatively gain insight into barriers and facilitators of an electronic QI intervention and presents experiences with the method from an ongoing case study to evaluate a QI system in the field of cardiac rehabilitation in the Netherlands.