Abstract The growing participation of developing countries in multilateral trade liberalization, as well as the boom of free trade agreements that grant exclusive preferences to its members, are both closely related to what has been denominated as 'open regionalism'. Additionally, this regionalism is associated with a process of 'deep integration' that transcends free trade issues. The concepts of 'deep regionalism' and 'open regionalism' do not have a precise definition and rather refer to a range of strategic decisions which governments might resort to in the process of regional integration. The first concept refers to the degree of sovereignty in economic policies that governments are willing to sacrifice in the design and implementation of national economic policies, especially when they try to harmonize national policies at a regional scale. The second relates to the relationship that will be established with countries that are left out of a preferential trade agreement. These new elements in trade diplomacy have stimulated a wide and heterogeneous literature dealing with projects of economic integration. In fact, for the first time, this literature increasingly includes comparative analysis of regions that such as Latin America and East Asia are believed to have similar experiences in their modern economic development. Sharing this general view, this paper seeks to explore the differences and similarities among the initiatives of regional economic cooperation, as they appear in the still scarce comparative studies on the subject. This implies dealing with three fundamental questions: (1); how can this sharp rise in regional integration projects be explained? (2); What is the 'depth' of its institutional design in terms of favouring major and more complex levels of economic integration between countries? And (3); why has each project defined itself as 'open regionalism', and thereby how have they justified their compatibility with the multilateral rules of the World Trade Organization (WTO);.