1 CONSTRUCTING AND CLASSIFYING INFORMAL INTERNATIONAL INSTITUTIONS QERIM QERIMI  Introduction This paper observes the phenomenology of the informal international structures. 1 It seeks to ascertain some key typological features based on such criteria as geography, power, problem, theme or issue, or a combination thereof. It seeks to obtain a more consolidated vision of fundamental characteristics of informal institutional structures. Such characteristics will be obtained by looking at the attributes that shape formal international structures. Operationally, they will be defined in terms of the indispensable elements of legitimacy and effectiveness. The ultimate aim is to provide a coherent framework of constructing and classifying informal international organizations.  This paper was presented at the 8 th Pan-European Conference on International Relations organized by the European Consortium for Political Research (ECPR) Standing Group on International Relations and European International Studies Association (EISA) and held in Warsaw, Poland, in September 2013. 1 The terms “institutions,” “structures” or “organizations” will be used interchangeably throughout this paper, same as “international organizations,” “intergovernmental organizations” or “international intergovernmental organizations.”