The article represents the methodological problem that concerns the hypothesis on the possibility to differentiate adjacent scientific directions — stylistics of scientific text and speech studies. The explanatory discourse approach (cognitive, discourse, stylistics) is based on the concept of functional stylistics that is being developed by the Perm Scientific School (Professor M. N. Kozhina). The hypothesis represents the semantic structure of scientific text correlated with its extralinguistic base. This base is concretized through scientific knowledge and defined with cognitive and communicative activities of a subject towards an object. The communicative and cognitive activities of a subject are complexes of extralinguistic factors that have different levels of abstraction in a particular epistemic situation. This level of abstraction is a methodological instrument that provides differentiation of those scientific directions. The stylistics has its own niche — research of language units as well as grammar and functional semantic categories in the framework of functional styles. These styles are influenced by abstract factors — public conscience, areas of activities, cogitation. The stylistics of scientific text is a fragment of modern functional stylistics, it deals with extralinguistic factors and text formation. Speech studies concern the research of unlimited dynamic space of speech and texts (not necessarily scientific ones). This space is interpreted according to dominant discourse factors (strong but not style-forming).