This invention relates to a process and system for cracking hydrocarbon feedstock containing vacuum resid comprising: (a) subjecting a vacuum resid to a first thermal conversion in a thermal conversion reactor (such as delayed coker, fluid coker, FlexicokerTM, visbreaker and catalytic hydro visbreaker) where at least 30 wt% of the vacuum resid is converted to material boiling below 1050 DEG F (566 DEG C); (b) introducing said thermally converted resid to a vapor/ lquid separator, said separator being integrated into a steam cracking furnace, to form a vapor phase and liquid phase; (c) passing said vapor phase to the radiant furnace in said steam cracking furnace; and (d) recovering at least 30 wt% olefins from the material exiting the radiant furnace (based upon the weight of the total hydrocarbon material exiting the radiant furnace).