本文試圖對歐盟東擴進行政治與經濟面向分析，並嘗試解答以下幾個問 題。第一，對歐盟新舊會員國而言，不東擴所需付出之政治考量（機會成本） 是促使歐盟向東擴張之主要原因；第二，經過估算後的成本效益分析，藉由東 擴所獲得效益仍大於東擴支出，且東擴支出以十年為期方式分攤，大幅降低經 濟衝擊；第三，東擴後的歐盟與波蘭政府咸需面對新挑戰，這些挑戰包括歐盟 未來整合與擴張能否持續、波蘭如何在歐盟内重新調適其國家利益與互動模式 等。

The author asserts that, first, in order to get a complete picture, not only of the easily quantifiable impacts but also of the intangible implications and the opportunity costs of non-enlargement must be taken into account. Second, the promise of eventual accession helps to secure social acceptance of painful reforms and to safeguard them from the influence of vested interests by increasing the costs of deviating from the reform path. In addition, by sharing the expenses of fifth eastward enlargement, the total cost is moderate. Third, the cost-benefit calculation is positive for both sides despite the fact that some areas and some industries of the new member states are going to suffer severely. Moreover, there will be obstacles and opportunities in the face of enlargement in both sides. It is worth noting that the development of new members in the EU is crucial. If new members could manage well inside the EU, they would reach the same level of western standard in decades; on the contrary, if this goal cannot be achieved, the split inside the EU is also foreseeable.