The objective of this proposal is to measure the effect of Foreign Direct Investment (FDI) on firm’s capital structure determinants in the post-liberalization era in the new twelve member states of the EU. The assumptions of this proposal are as follows: (i) firm’s that have attracted FDI in the post-liberalization period have had access to international capital markets, (ii) optimized their capital structure mix faster and (iii) had overcome liquidity constraints better than firms without FDI due to their foreign investors in developed markets. Accordingly, we are proposing to examine the capital structure determinants of firms that have attracted FDI (FDI firms) and that have not (Non-FDI firms), in the post liberalization period for determining structural differences. The findings will reveal not only the differences of capital structure determinants of firms but also if FDI facilitated the integration process between EU-15 and the new member states. To our information this approach has not been studied in the set of emerging markets especially for the new twelve member states of the EU and will enable observing how capital structures take shape once FDI is injected. If findings confirm the given expectations, this study can be used as a risk management tool for a more strategic and efficient allocation of EU funds both to new member states and to candidates states of South Eastern Europe for the purpose of integrating them to EU-15, to European Monetary Union in line with the Stability Pact and even contribute to the newly released Neighborhood policy.