The effect of the inflow of foreign direct investment (FDI) can be investigated with the theory of international production offering useful insights into the expansion of firms in foreign countries, which can also be applied to host countries undergoing economic transformation-in this paper's case, Poland. A thorough analysis of changing FDI inflows (and inward stocks) and its various patterns, as well as their impact on the Polish economy, has disclosed certain nuances of evolving FDI contribution and effects on the processes of transformation and, to some extent, on economic development and European Union regional integration. The conclusion is that it was not just the transition of the Polish economy but, rather, a complex and long-term process of systemic transformation that attracted FDI in the 1990s, and to which FDI and foreign-capital companies have made significant contributions. However, the contribution of FDI and transnational corporations in changing the stage of Poland's economic development is insufficient.