The article analyzes the development of the research of late scholastics sources of Descartes' theory of ideas. In the first part, it analyzes long time dominant opinion among the historians of philosophy that Descartes' theory of ideas is an epistemology in its essence. The reasons for abandoning of such, mainly neokantian image were the appearance of the new generation of the historians of philosophy that investigated the non-metaphysical areas of Descartes' thought, as well as the new interpretations of the very late scholastics philosophy. In second part of the essay, it is shown why late scholastics is relevant for Descartes, and not, for example, Tomas Aquinas and why Francisco Suarez is especially important in the context of Descartes theory of ideas.