Solid depositions from thermal stressing of a jet fuel model compound, n-dodecane (Dod), is studied in the presence of three initiator additives, 1-nitropropane (NP), triethylamine (TEA), and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (TEMPO), to show the role of initiators in the carbon deposition because of thermal cracking of jet fuels. It is found that the thermal cracking rate of Dod is enhanced by the initiators in the following order: TEMPO > NP > TEA and that TEMPO and TEA remarkably inhibit the formation of pyrolytic deposit by 30-50% at a similar conversion level. Temperature-programmed oxidation (TPO) of deposits indicates that reactive deposition is improved slightly by TEMPO and TEA but the less reactive deposits are reduced because of possible radical scavenging or the hydrogen donation effect, resulting from the decomposition of TEMPO and TEA. Scanning electron microscopy (SEM) shows that TEA and NP also have a significant effect on the deposit morphologies. Those results are also observed in the thermal stressing of Chinese RP-3 jet fuel with initiators.