Service-oriented ERP systems promise to allow for a fine-grained alignment of IT with the specific functional requirements of an organization's business processes. In this regard, studies particularly emphasize the potential to flexibly exchange services by means of market-based transactions. One important aspect widely neglected, however, is the endeavor of governing the implementation process of this new kind of information systems. Having applied New Institutional Economics, our research reveals that this implementation process, on the contrary, even calls for rather hierarchical modes of governance. However, different types of activities relevant to implementing a service-oriented system have to be taken into account. Hence, in this paper we present a set of criteria enabling organizations to classify these activities in more detail and to choose a suitable mode of governance. We demonstrate the approach by means of an example and indicate directions for future research.