Designing has assumed a prominent position in current regional planning and development. There is, however, no coherent body of knowledge on how designing contributes to, alters or influences planning processes. Our essay explores a leading example: the contributions of designing to Dutch regional planning and development, and identifies topics for scholarly research that will improve the understanding of design approaches in planning and advance regional design practice. We interviewed stakeholders involved in Dutch regional planning practice and identified eleven contributions of designing: four to the content and seven to the process of planning. An exploration of scholarly literature in landscape architecture and urban design added more depth and understanding to these contributions. We conclude that the long-term scope of regional design means its impacts must also be evaluated over the long term. Moreover, stakeholder involvement in a design process draws attention to the political aspects of designing and the need to develop skills to balance multiple interests. Finally, as designing and planning are never the same in different situations, empirical research and design experiments in different planning settings can reveal which characteristics determine the potential of designing in different planning contexts.