One central and important requirement for IS project portfolio selection is the adequate consideration of project interactions. However, the IS discipline notably lacks a common understanding of the nature of project interactions and their impact on IS project portfolio selection. To remedy this we conduct a systematic and interdisciplinary literature review thereby providing a starting point for a cumulative research tradition. The main contribution of this paper is the development of a taxonomy to summarize the current state-of-the-art. Thereby, we provide a basis enabling researchers to develop integrated approaches. Based on the identified research gaps we formulate a research agenda for the field of IS project portfolio selection considering interactions.