A process for converting a high-boiling hydrocarbon feedstock into lighter boiling hydrocarbon products, said lighter boiling hydrocarbon products being suitable as feedstock's for petrochemicals processes, said converting process comprising the following steps of: feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking units, wherein the cascade of hydrocracking units comprises at least two hydrocracking units cracking said feedstock in a hydrocracking unit, separating said cracked feedstock into a stream comprising hydrogen, a stream comprising a light boiling hydrocarbon fraction and a bottom stream comprising a heavier hydrocarbon fraction feeding said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein the process conditions in each hydrocracking unit are different from each other, in which the temperature conditions from the first to the subsequent hydrocracking units increases, wherein the reactor type design of the last hydrocracking unit in said cascade of hydrocracking units is of the slurry phase type, and sending the light boiling hydrocarbon fractions from each hydrocracking unit to petrochemicals processes, comprising at least a gas steam cracking unit and one or more units chosen from the group of pentane dehydrogenation unit, propane dehydrogenation unit, butane dehydrogenation unit and mixed propane-butane dehydrogenation unit, further comprising separating said light boiling hydrocarbon fractions into a stream comprising C1, a stream comprising C2, a stream comprising C3 and a stream comprising C4 and feeding said stream comprising C3 to a propane dehydrogenation unit and feeding said stream comprising C4 to a butane dehydrogenation unit. further comprising feeding said stream comprising C2 to a gas steam cracker unit. feeding a heavy hydrocarbon feedstock to a cascade of hydrocracking units, wherein the cascade of hydrocracking units comprises at least two hydrocracking units cracking said feedstock in a hydrocracking unit, separating said cracked feedstock into a stream comprising hydrogen, a stream comprising a light boiling hydrocarbon fraction and a bottom stream comprising a heavier hydrocarbon fraction feeding said bottom stream of such a hydrocracking unit as a feedstock for a subsequent hydrocracking unit in said cascade of hydrocracking units, wherein the process conditions in each hydrocracking unit are different from each other, in which the temperature conditions from the first to the subsequent hydrocracking units increases, wherein the reactor type design of the last hydrocracking unit in said cascade of hydrocracking units is of the slurry phase type, and sending the light boiling hydrocarbon fractions from each hydrocracking unit to petrochemicals processes, comprising at least a gas steam cracking unit and one or more units chosen from the group of pentane dehydrogenation unit, propane dehydrogenation unit, butane dehydrogenation unit and mixed propane-butane dehydrogenation unit, further comprising separating said light boiling hydrocarbon fractions into a stream comprising C1, a stream comprising C2, a stream comprising C3 and a stream comprising C4 and feeding said stream comprising C3 to a propane dehydrogenation unit and feeding said stream comprising C4 to a butane dehydrogenation unit. further comprising feeding said stream comprising C2 to a gas steam cracker unit.