The problem of adequately measuring success of information system (IS) projects has not been sufficiently solved. Whereas the traditional approach of assessing IS project success in terms of adherence to budget, schedule and requirements is said to be insufficient, there is lack of agreement on a multidimensional approach using further or different criteria. As success is seen as matter of perspective, project stakeholders’ subjective perceptions of project success are supposed to be important criteria. Thereby, especially the satisfaction of the client organisation is relevant as it is crucial for the contractor’s reputation and assignments of follow-up projects. However, IS developing companies and success reports predominantly assess IS project success using only the objective adherence-to-planning criteria. We believe that client satisfaction in IS projects highly depends on the confirmation of client’s expectations concerning project (process and product) performance. We thus apply the Expectation-Confirmation Theory (ECT) to the context of IS projects aiming to explain the satisfaction of the client organisation. As managing expectations may influence satisfaction, we extend the ECT by client-vendor communication. We assume that client-vendor communication manages expectations, that is, it moderates the relationship between expectation and confirmation. We present and argue for our hypothesized model and according measures for a quantitative analysis. As our study is one of few focussing on the client perspective, we propose an innovative approach to further improve the understanding of IS project success.