Mental models are basic cognitive constructs that are central for understanding phenomena of the world and predicting future events. Our comparison of two analysis approaches, SMD and QFCA, for measuring externalized mental models reveals different levels of abstraction and different perspectives. The advantages of the SMD include possibilities for statistical testing of single criteria and big groups. Its disadvantages include a comparatively low pedagogical expressiveness of the more formal criteria. An analysis of single cases with the help of QFCA avoids imprecision by virtue of many steps of analysis and seems more significant on a qualitative level. The main limitation of QFCA is that comparisons are possible for small groups or knowledge sections only. The content-based results open various possibilities for comparing mental-model representations by single cases or groups with different pedagogical implications. (Contains 8 tables and 7 figures.)