Divergences between perception and measurement of information system (IS) project success are phenomena known as successful failures or failed successes. Such projects either satisfy stakeholder expectations or are completed according to their plans, but do not succeed in both terms. Based on expectation-confirmation theory, we advance the understanding of project success by observing the role of client-vendor communication regarding the interaction of client expectations, perceptions, and satisfaction. By means of a quantitative field study with managers of IS projects on the client side, we show that perceptions of product performance are more relevant than perceptions of process performance for meeting client expectations in IS projects. Expectations towards the process (i.e., budget and schedule) are revealed to be considerably less relevant, which is a likely consequence of many projects failing to meet such expectations. An avenue for future research resulting from our study is the investigation of differences concerning communication mediums by contrasting agile and non-agile development projects.