Ševčenko has contributed to two connected yet distinct disciplines, Byzantine, Slavic studies, and Ukrainian Studies. His work addresses Byzantine written culture and society from the Late Antique period to the 15th century and explores contact between the Slavic world and Byzantium from the medieval to the early modern period. Ševčenko has written on philology, literature, epigraphy, paleography and codicology. He was noted for the engaging, "detective novel" style of his prose, as in his famous article “The Date and Author of the So-Called Fragments of Toparcha Gothicus”, which reveals that the text considered the earliest surviving narrative source on the history of the Kievan Rus’ is a 19th-century forgery crafted by its “discoverer” and editor Carl Benedict Hase.