This dissertation examines a particular type of donor behaviour – known as country earmarking of contributions – which occurs within the voluntary financing system of the specialised agencies of the United Nations. Based on a dyadic donor-recipient aid allocation model, my research demonstrates that already during the 2000-2014 period of the Millennium Development Goals (MDG), a large share of the voluntary multilateral funding decisions was strongly influenced by the commercial priorities of the OECD donor countries. The theoretical contribution of this dissertation focuses on disentangling the mix of policy advantages that the donor countries are able to pursue through linking of their commercial priorities with development cooperation programmes implemented by specialised UN institutions. The findings of this research have a number of important implications for the neutrality of key normative functions in the specialised UN agencies, especially those concerned with the creation and oversight of international norms and standards. They also imply the existence of significant practical constraints to the feasibility of the proposed financing reform of the UN Development System.