This paper presents the results of the study of the composition of cracking products of high-sulfur tar obtained from oil of Zyuzeyevskoye field in the presence of radical-forming additive – didodecanoyl peroxide. Thermal treatment of the mixture of vacuum residue with different amounts of didodecanoyl peroxide was carried out at a temperature of 500 °C. The duration of the process was 15 min. Characteristic features of changes in the material balance of the process, group composition of liquid cracking products, qualitative and quantitative composition of newly formed sulfur compounds were established. The use of additive in the amount of 0.5 – 0.75%wt. allows to reduce thermal stability of high-molecular components of tar (resins and asphaltenes), and also promotes change in direction of reactions. Processes of condensation of resins and asphaltenes into solid coke-like products are slowed down, and cracking reactions are initiated with formation of low-molecular components, which fall into the composition of oils, as a result of which it is possible to obtain additional amounts of distillate fractions. It is shown that thiophene, benzo- and dibenzothiophene derivatives, which are absent in the initial tar, are intensively formed and accumulated in the composition of liquid cracking products, which worsens the quality of the obtained distillate fractions. Among the identified sulfur compounds benzothiophene homologs prevail. It was found that cracking of tar in the presence of additive didodecanoyl peroxide promotes deep destruction of sulfur-containing fragments of vacuum residue and asphaltene molecules. Sulfur compounds formed under these conditions not only get into the composition of oils, but also participate in condensation reactions with the formation of solid products, which leads to an increase in the degree of sulfur removal from the composition of liquid cracking products. For citation: Goncharov A.V., Krivtsov E.B. Effect of didodecanoyl peroxide on transformations of high-sulfur vacuum residue components in the process of initiated cracking. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 121-128. DOI: 10.6060/ivkkt.20246708.15t.