Against the background of limited resources, interdependent and interrelated political decision-making, and a better understanding of complex challenges related to sustainable development, policy coherence for development (PCD) has emerged as a key concept in international relations. Based on literature review and qualitative interviews with experts from the OECD, the EU and academia, the first part examines the theoretical background of the PCD concept. It finds that the PCD concept itself remains a very controversial issue despite increasing references at national, regional and international level. The second part analyses those conceptual and practical problems in greater detail, focusing on a) the understanding of development; b) balancing divergent goals; and c) institutional mechanisms. It draws on comparative qualitative research undertaken in Germany and France from 2013 to 2014 to illustrate different dimensions of PCD. Finally, the paper offers thoughts on a new framework for measuring and analysing PCD at national level.