No single information systems development method (ISDM) suits to all information systems development (ISD) projects. Despite of this, ISDM selection has received limited attention in earlier research. This raises the question are ISDM selection decisions rare in practice as well, and if so, what are the reasons. We used the bounded rationality and functional stupidity theories to investigate ISDM selection decision- making behavior, and interviewed 31 IS professionals working in the borderline between IS clients and suppliers. We examined their experiences about ISDM selection within both types of organizations. We discovered that the ISDM selection decisions of ISD projects are seldom discussed, that the ISDM selection behavior of client and supplier organizations differ, and that the bounded rationality and functional stupidity theories are descriptively useful. In addition to these research contributions, our study shows that there are theoretical and practical reasons to develop better ISDM selection guidelines for ISD projects.