We use the MEOS model to assess the possible impact of Polish unconventional gas (UNG) production on natural gas flows through the Czech Republic, Hungary, Poland and Slovakia. MEOS is a network flow optimization model designed to solve the minimum-cost flow problem in a network that consists of nodes (production areas, consumption areas, transshipment junctions) and arcs (pipelines). The article postulates and analyzes five distinct scenarios combining various levels of UNG production with different settings of regional infrastructure. The MEOS simulations reveal the critical importance of currently missing cross-border links between the countries. Polish UNG production is therefore likely to trigger new infrastructure projects and foster the ones that are currently under consideration. The biggest changes in natural gas supply can be expected in Slovakia and Hungary, as these markets do not have direct access to German hubs. Similarly, it is reasonable to expect Polish UNG to be traded at the Austrian CEGH hub, which will further catalyze the transformation of the regional market. It is further argued that in addition to sufficient infrastructure, UNG production will require liberalization of the Polish domestic market and a certain degree of integration of regional markets, effectively changing the nature of natural gas trading in the region, which is still dominated by Russian long-term, take-or-pay contracts.