On the basis of an empirical study, this article offers some generalisations concerning service systems characteristic of split towns in East-Central Europe. Three frontier urban complexes were examined, including two in the Polish-German borderland, viz. Słubice (Poland) – Frankfurt on the Oder (Germany) and Gubin (Poland) – Guben (Germany), and one in the Polish-Czech borderland, viz. Cieszyn (Poland) – Český Těšín (Czech Republic). The model approach adopted was intended to ensure an insight into the basic properties of the service system in the form of significant factors and connections holding within it. There are many factors giving shape to a service system, but those primarily responsible for differences between the service systems of the examined frontier urban complexes include: (a) the kinds of services offered, (b) specific forms of retail trade, (c) intensity of transborder traffic, and (d) consumers of services. Their unique combination allowed for distinguishing two service systems: in the Polish-German borderland and in the Polish-Czech one. The research also revealed that each system had a double service practice. One, geared to the service of the local population, is fairly stable, and the other – geared to a transborder customer – is different. In the Polish-Czech borderland it is balanced, equally open to the local customer and one from abroad, while in the Polish-German borderland it displays a marked asymmetry in terms of volume and function.