Cross-border cooperation to promote economic development and political integration has been among the EU's key themes since the 1990s, and contemporary policy networks are considered useful organisational solutions. Focusing on transport policies in the border regions of Basel and Luxembourg, we analyse the persistency of national preferences among policy actors, mapping their perceived 'policy spaces of action' and conceptualising these policy spaces as relational. We discuss that the networks' various actors on either side of the border appear to perceive the actual 'policy spaces' very differently. Therefore, and due to the networks' terminability, these policy spaces are highly contested and frequently negotiated between the actors. Based on a combination of in-depth interviews, sketch maps, and social network analysis, we show that large spatiocultural differences still prevail among network actors, potentially impacting on the decisions taken in cross-border policy networks.