Interreg has been the European Union (EU) initiative to support territorial cooperation and integration across borders. 30 years of Interreg, though, have not changed the fact that different barrierspersist at the inner borders of the EU, and that only a few cross-border territories have emerged as joint action spaces with in-depth political cooperation and people’s interaction. While it is consensus thatcross-border economic flows are decisive for the development of functional and in the end institutionalized cross-border regions, regional econometric models demonstrate the persistence of border barrierswithin the EU, but also that the removal of these barriers greatly increases regional growth potential. In a research project focusing on the alignment of cross-border regional economic interests, cross-bordernetworks between business and politics and cross-border policies in the Danish-German cross-border region Sønderjylland-Schleswig we have discovered issues on different communication codes between businessand politics, lack of tangible cross-border development strategies and a lack of alignment of shortterm, time delimited Interreg project oriented operational programs to tangible, long-term strategies ofcross-border regional economic development. EU territorial cohesion policies could be better aligned with long-term, cross-border economic strategies to create sustainable cross-border development. It will beimportant to rethink Interreg in a less project-oriented, but more strategy-oriented direction; focusing on flows and institutional settings promoting the development of flows by reducing cross-border barriers.