Information systems development (ISD) often fails. Requirements engineering (RE) problems rank high in ISD project failure statistics. RE is often regarded as the link between business (processes) (BP) and IS. Thus, in RE, the BP and IS requirements need to be synchronized. We conducted three case studies to investigate RE problems and the reasons for them, especially to contemplate how to synchronize business process and IS development requirements in plandriven  (waterfall) and change-driven (agile) projects. Investigated cases indicate that the ontological and epistemological matching of IS and BP requirements engineering methods improves requirements quality.