The paper has the dual objective of contributing to theory development as well as to the debate about the added value of EU Cohesion Policy. Experimentalist governance theory suggests that a virtuous feedback loop between policy design and implementation can the input- and outputlegitimacy of policy making. EU Cohesion Policy formally resembles this experimentalist setting, but persistent debates about its added value suggest that the virtuous loop is blocked. The paper uses new institutionalism theory to systematically identify theoretical explanations for this blockage. It argues that the experimentalist link between organizational structure, pooling of experiences, greater participation, and policy learning is highly precarious. First, the rational-choice perspective suggests that the link rests on the optimistic assumption of a common utility function among the participating actors. Moreover, the structural funds provide strong incentives for grantseeking. Second, the discursive perspective shows that the identification of shared interests depends on highly demanding speech conditions. Third, the sociological perspective highlights that the evaluation of information is socially conditioned. Therefore, learning may be based on fallacious assumptions and lead to undesired results. The paper substantiates these insights with empirical evidence from one case of institutionalized crossborder cooperation in East Central Europe.