The aim of the article is to define the extent and nature of the scope of the discipline of international relations. It is our belief that this is the key factor determining its status as an academic discipline. This article addresses the ontological criteria for delimiting the discipline, and in this sense it continues certain threads presented in the article titled The Subject, Theory and Methodology of the Science of International Relations, published in Issue 1/2015 of “Stosunki Międzynarodowe – International Relations”. The thesis formulated for the purpose of the article comes down to the statement that delimitation of the scope of the discipline of international relations is performed on the basis of an assumption on the level of ontology. Only on this basis can we formulate a further assumption, on the level of epistemology (theory). In other words, the question: ‘What do we study?’ precedes another question: ‘How to study it?’. In the article the author proposes the application of the following criteria of delimiting the scope of the discipline of international relations: the institutional basis of this discipline, reconstruction of the notion of internationality, the level of analysis, subdisciplines.