Presented study was a part of ESPON TERCO project (European Territorial Cooperation as a Factor of Growth, Jobs and Quality of Life) and was aimed at verifying the hypothesis that territorial cooperation underpins socio-economic development. Based on the literature review a conceptual model of successful territorial cooperation was proposed, where this kind of cooperation was defined as bringing the highest joint socio-economic development to the cooperating territorial units. That theoretical model was verified empirically by structural equation modeling, based on data collected via electronic questionnaires (CAWIs) in 9 cross-border case studies. The results of the SEM analysis positively verified the main hypothesis and provided information about the role of particular ‘determinants and factors’ in achieving successful TC measured by several ‘impact’ indicators. It was also possible to access the extent to which particular ‘determinants and factors’ contributed to the successful TC as a whole and its particular ‘impacts’. The probability of success of territorial cooperation was the highest when TC projects were initiated by NGOs, local or regional government, funding came from own or EU sources, cooperation was based on simple forms of collaboration, and related to culture, economy, tourism, natural environment or physical infrastructure