Resumen. Developing a comprehensive understanding for analysing the relational structure of border regions necessitates the evaluation of different dimensions of socio-spatial interaction, regarding the border permeability. In this framework, the relationships emerging at the borders of national and supranational bodies can be measured under four different categories of economic, social, political/administrative and spatial. These dimensions identify the permeability of borders by exploring how borders separate or connect each side. Within this context, this study redefines borders non-normatively by using their separation and connection attribute related with their permeability characteristics. It also analyses the changing characteristics of borders from physical barriers to border regions considering socio-economic and socio-spatial interaction. As an empirical study, socio-spatial interactions that define the selective permeability among supranational bodies, nation states and border regions are investigated at the EU (Bulgaria and Greece) and Turkish borders by conducting in-depth interviews with actors who have cross border relations.