A process for cracking hydrocarbon feedstock comprising at least one sulfur-containing compound comprising: heating the feedstock and a peroxide-containing compound, mixing the heated feedstock and peroxide-containing compound with a fluid and/or a primary dilution steam stream to form a mixture, flashing the mixture to form a vapor phase and a liquid phase which collect as bottoms and removing the liquid phase, separating and cracking the vapor phase, and cooling the product effluent, wherein the oxidized sulfur-containing species are removed as bottoms