The Hsl-Zuid, the Iron Rhine, the deepening of the Scheldt, the widening of the Grensmaas: these are examples of major cross-border infrastructure projects. The generally very good relationship between the Netherlands and Flanders often suffers as a result. What are the characteristics of such large cross-border projects? What are related success and failure factors? How can the decision-making around these projects be improved to ensure their quality and to ensure that they strengthen rather than burden the relations between the Netherlands and Flanders? Based on the experiences with the Hsl-Zuid, the Scheldt and the Iron Rhine, this study draws some lessons.