A process for the refining of crude oil with at least one atmospheric distillation unit for separating the various fractions, a sub-atmospheric distillation unit, a conversion unit of the heavy fractions obtained, a unit for enhancing the quality of some of the fractions obtained by actions on the chemical composition of their constituents and a unit for the removal of undesired components, where the sub-atmospheric distillation residue is sent to one of the conversion units, the conversion unit includes at least one hydroconversion reactor in slurry phase, into which hydrogen or a mixture of hydrogen and H2S, is fed, in the presence of a suitable dispersed hydrogenation catalyst with dimensions ranging from 1 nanometer to 30 microns.