A process for upgrading refinery heavy hydrocarbons to petrochemicals, comprising the following steps of: (a) feeding a hydrocarbon feedstock to a ring opening reaction area, wherein the process conditions prevailing in said reaction area for ring opening are a temperature from 100 °C to 500 °C and a pressure from 2 to 10 MPa together with from 50 to 300 kg of hydrogen per 1,000 kg of feedstock over an aromatic hydrogenation catalyst and passing the resulting stream to a ring cleavage unit at a temperature from 200 °C to 600 °C and a pressure from 1 to 12 MPa together with from 50 to 200 kg of hydrogen per 1000 kg of said resulting stream over a ring cleavage catalyst; (b) feeding the effluent from (a) to a separation unit for producing a gaseous stream comprising light boiling hydrocarbons, a liquid stream comprising naphtha boiling range hydrocarbons and a liquid stream comprising diesel boiling range hydrocarbons; (c) feeding said liquid stream comprising naphtha boiling range hydrocarbons to a hydrocracking unit, wherein the process conditions prevailing in said hydrocracking unit are a reaction temperature of 300-580 °C, a pressure of 0.3-5 MPa gauge, and a Weight Hourly Space Velocity (WHSV) of 0.1-10 h-1; (d) separating reaction products of said hydrocracking unit of step (c) into an overhead gas stream, comprising light boiling hydrocarbons, and a BTX (a mixture of benzene, toluene and xylenes) comprising bottom stream, (e) feeding the overhead gas stream from the hydrocracking unit of step (d) and the gaseous stream from the separation unit of step (b) to a steam cracking unit and at least one or more units chosen from the group of propane dehydrogenation unit, butane dehydrogenation and combined propane-butane dehydrogenation unit, preferably after separating a hydrogen containing stream from said gas streams. (a) feeding a hydrocarbon feedstock to a ring opening reaction area, wherein the process conditions prevailing in said reaction area for ring opening are a temperature from 100 °C to 500 °C and a pressure from 2 to 10 MPa together with from 50 to 300 kg of hydrogen per 1,000 kg of feedstock over an aromatic hydrogenation catalyst and passing the resulting stream to a ring cleavage unit at a temperature from 200 °C to 600 °C and a pressure from 1 to 12 MPa together with from 50 to 200 kg of hydrogen per 1000 kg of said resulting stream over a ring cleavage catalyst; (b) feeding the effluent from (a) to a separation unit for producing a gaseous stream comprising light boiling hydrocarbons, a liquid stream comprising naphtha boiling range hydrocarbons and a liquid stream comprising diesel boiling range hydrocarbons; (c) feeding said liquid stream comprising naphtha boiling range hydrocarbons to a hydrocracking unit, wherein the process conditions prevailing in said hydrocracking unit are a reaction temperature of 300-580 °C, a pressure of 0.3-5 MPa gauge, and a Weight Hourly Space Velocity (WHSV) of 0.1-10 h-1; (d) separating reaction products of said hydrocracking unit of step (c) into an overhead gas stream, comprising light boiling hydrocarbons, and a BTX (a mixture of benzene, toluene and xylenes) comprising bottom stream, (e) feeding the overhead gas stream from the hydrocracking unit of step (d) and the gaseous stream from the separation unit of step (b) to a steam cracking unit and at least one or more units chosen from the group of propane dehydrogenation unit, butane dehydrogenation and combined propane-butane dehydrogenation unit, preferably after separating a hydrogen containing stream from said gas streams.