This paper reviews what has been done and what should be done at the G20 Summit meetings and suggests key agendas to be focused on for the Seoul Summit so that the G20 Summit can genuinely become the premier forum for international economic cooperation. First, the G20 leaders must address the problem of global imbalances even though it is very sensitive and politically difficult. But naming and shaming must be avoided and more balanced and comprehensive discussions will be needed. Second, regarding financial reforms, the Seoul Summit should focus more on follow-up agendas than on new ones and announce a comprehensive action plan that includes country-specific commitments. Third, given that the IMF reform has quantitative targets and that the G20 leaders pushed forward the deadline twice for the quota reform, this agenda of the IMF reform is symbolic. Thus the G20 leaders must conclude the issues of IMF quota and governance reforms by agreeing on details. Fourth, Korea will propose the agenda of global financial safety nets as a Korean initiative at the Seoul Summit. However, discussions and suggested ideas up to now are insufficient to tackle the intrinsic problem of capital flow volatility. The G20 Summit should be committed to reducing volatile movement of international capital by introducing direct and pre-emptive measures. Fifth, at the Seoul Summit the G20 leaders need to show some progress to break the current impasse of trade negotiations so that its credibility can be greatly enhanced. Sixth, the G20 leaders must recognize that development agenda is morally important and that addressing development issues will strengthen the legitimacy and leadership of the G20. For the success of the development agenda, the multi-year action plans prepared by the Working Group need to be adopted by the Leaders and must further be carried on by the G20 Paris Summit in 2011 and the Mexico Summit in 2012. Last but not least, to overcome those challenges regarding legitimacy issues, characteristics issues, institutionalization issues, and relationships with international organizations and successfully achieve its ultimate goal, the G20 must establish an effective implementation mechanism and this specific matter should be discussed at the G20 Summits in Seoul as well as in Cannes in 2011.