This study focuses on the analysis of East Asian regionalization from the perspective of one country ‒ South Korea (hereinafter Korea). If economic integration in East Asia is presented mainly through the prism of rivalry between China and Japan or the leading role of ASEAN, then the importance of Korea in the process of East Asian regionalization may be unjustifiably neglected. This study is therefore aimed at placing Korea in the development of regionalization in East Asia in the 21st century, and in particular at answering the question of how Korea's position has evolved in intra-regional trade, foreign direct investment and regional value chains in East Asia after the year 2000. The results of the research undertaken indicate that Korea's position in the development of East Asian regionalization is evolving. Firstly, in the area of foreign trade, the importance of Korean exporters in intra-flows increases, while the country's share in imports decreases. Secondly, Korean investors are more active in the countries of the region, but the share of that country as a recipient of direct investment is decreasing. Thirdly, Korean firms are largely integrated into global and regional production chains. The main problem for economic policy that has been identified in the study is extremely high concentration on selected markets and in selected sectors. This creates an excessive dependence of a large part of the South Korean economy, and thus the possibility of maintaining economic growth dynamics on external factors (e.g. decisions taken by the most influential partner countries or the current situation in the most important sectors). Taking more intensive measures to reduce this dependence is the most significant recommendation for Korean economic policy resulting from the analysis carried out in the study.