The present work focuses on the evaluation of the effect of the presence of SO2 on the formation of soot from ethylene pyrolysis. The work includes the experimental study of ethylene pyrolysis in the presence of different amounts of SO2 in a quartz flow reactor, at atmospheric pressure in the temperature interval of 975-1475 K, and the kinetic modeling study of the gas-phase process involving the ethylene-SO2 interactions. Soot and main gas products (i.e. C2H4, SO2, C2H2, H-2, CO, CO2, CS2 and COS) have been quantified, and the results have been subsequently analyzed and related their evolution trends as a function of temperature and inlet SO2 concentration. The mechanism used for calculations has been progressively modified and updated along this work in relation to the present gas-phase experimental data, and a subset for describing the possible hydrocarbons-sulfur compounds interactions is proposed. The updated chemical kinetic mechanism provides a general good description of the gas phase experimental results of the present work. The main results attained indicate that the presence of SO2 in the initial mixture has direct implications on soot formation, and different soot and SO2 reduction levels as a function of the reaction environment (i.e. temperature and inlet SO2 concentration) are achieved. The diminution in the production of soot occurring in the presence of SO2, compared to the pyrolysis of pure ethylene, has been related to the occurrence of both hydrocarbons-sulfur compounds interactions and oxidation reactions, the latter experimentally supported by the quantification of CO, CO2 and CS2. Additionally, elemental and type of sulfur analyses of the soot samples revealed the presence of sulfur bonded to soot structure. (C) 2015 Elsevier Ltd. All rights reserved.