Summary: In recent years computer algebra systems (CAS) have become an integrated part of the upper secondary school mathematics program. Despite the many positive possibilities of CAS, there also seems to be a flip side of the coin in relation to actual difficulties in learning mathematics, not least because a strong dependence on CAS for mathematical processes can challenge mathematical concept formation. Using selected classical mathematics education frameworks we search for an explanatory model of phenomena observed by teachers. It is concluded that pragmatic solution strategies and non-reified concepts lead to what we describe as CAS-instrumental understanding, and hence CAS-induced difficulties in learning mathematics.