The regional situation in Eastern Europe changed significantly by the end of the first decade of the 21st century. Competitionbetween Russia and the European Union increased during the 2000s, while at the same time both actors were changing their approach to the six states of the former USSR that lie between Russia and the EU – Azerbaijan, Armenia, Belarus, Georgia, Moldova and Ukraine. In order to widen and deepen their influence on those territories and to reduce uncertainty about their regional politics, Moscow and Brussels developed their own integration projects and demanded those post-Soviet states define their position in the EU-Russia competition. Russian and European scholars, when trying to analyze the future of the Post-Soviet Six states, mostly examine the attractiveness of the two integration projects. While important, such an approach is insufficient, as it ignores the individual internal environments. To assess the prospects for Russia’s Eurasian Economic Union and the EU’s Eastern Partnership, however, one must look inside the six states, which are so important for both Moscow and Brussels. This article explores the aspects of the European and Eurasian integration projects that may be attractive to the six states. Within this framework, it considers what and how elements of those states’ internal environment might influence their choice by examining and comparing both integration projects. It proposes focusing directly on the countries that are currently facing the dilemma of integration and are expected to choose. Despite a number of internal factors influencing the states’ integration behaviour, research has shown that in such circumstances, a choice (whether it is made) cannot be considered final, given the individual internal environments of the Six. Their further integration will require additional mechanisms of stimulation, which will need to be developed by the centres of integration — namely, Moscow and Brussels.