The success of Information Systems (IS) projects is of great relevance in IS research and practice. However, scholars barely agree on a definite set of IS project success factors. In order to gain insights into such success factors, we conducted an empirical qualitative study. We interviewed eleven experienced project managers concerning the factors which have influenced the success of their IS projects. In the data collection, we used the Repertory Grid Technique and extended it by 'Laddering'. Having collected a total of 78 unique factors from the interviews, we applied content analysis to categorize the factors and arrange the emerging 19 categories hierarchically in a causal map via cognitive mapping. We contribute to developing a list of IS project success factors.