The article discusses the relationship between the liberalization of the gas market and the security of gas supply. The issue is considered in the context of two interlinked factors, the geographical factor and the geopolitical factor, which determine the structure and functioning of the gas sector in EU member states. The geographical factor, i.e. the fact that gas resources are predominantly located in non-European countries, implies the dependence of European countries on gas supplies. The geopolitical factor, on the other hand, is used a means of political leverage by gas exporting countries, including Russia. Taking these two factors into account, the author sets out to determine whether Europe’s dependence on gas imports puts gas supplies at risk and whether or not it could become an obstacle to the full liberalization of the gas market. This question is related to the hypothesis that the relatively slow liberalization of the EU gas market, compared with the electricity market, for example, is due to fears that unbridled liberalization could have an adverse impact on the security of supplies. The analysis is especially topical in the context of reports about a revolution on the U.S. gas market triggered by a technological breakthrough in the extraction of shale gas. If these reports are confirmed, the author says, shale gas may redefine the relationship between the security of gas supplies and the degree of liberalization of gas markets in EU countries.