Abstract In this study, we investigate hedges, boosters and self-mentions as main expressions of epistemic positioning and how much they are projected by explicit authorial presence in the research writings by Chinese PhD students and expert writers across four science disciplines. Results show that PhD science students used considerably more hedges, boosters and self-mentions than journal article writers. They exhibit an obvious preference for certain epistemic resources and an avoidance to hedge or boost their/others’ claims in their academic writings. The results are discussed with regard to different cultures, disciplines and writer groups, and pedagogical implications on L2 research writing instructions are also raised at the end of the chapter.