Although the question of relationship between basic concepts of traditional ontology and central concepts of fundamental ontology is not a topic which is systematically dealt with in Being and Time, it is obvious that some of the theses which are crucial not only for Heidegger's interpretation of philosophical tradition, but also for the whole project of fundamental ontology, concern this 'conceptual scheme'. In fact, the backbone of Heidegger's critical confrontation with dominant philosophical conceptions is the question of relationship between the concept of 'substance' and the concept of 'Being', i.e. the discussion of philosophical doctrines in which 'Being' is reduced to 'substance'. Besides this context, which concerns the ontological problematics in the strict sense, it is possible to show that the refutation of the basic categories of traditional ontology is an issue which has a decisive role in more concrete phases of the realization of the project of fundamental ontology. This is especially confirmed in Heidegger's discussion of the concept of 'Being-There'. The interpretation of Heidegger's treatment of the relationship between the concepts of 'Being-there', 'existence' and 'existentials' on the one hand, and the concepts of 'substance', 'essence' and 'categories' on the other, shows that one of Heidegger's basic theses is that a transformation of concepts of traditional ontology is necessary for an appropriate understanding of human being.