Abstract: Materials and methods for inhibiting the formation of filamentous coke on heated metal surfaces. Organoselenium compounds, including diarylselenides, diaryldiselenides, alkylarylselenides, and alkylaryldiselenides, are employed as hydrocarbon feedstock additives or as hydrocarbon fuel additives to inhibit filamentous coke formation on hydrocarbon processing systems, including reactors, furnaces, engines and parts thereof and in particular to inhibit filamentous coke formation on heat-exchangers in such systems.