A dual-fuel burner for use in furnaces such as in steam cracking. The burner includes a primary air chamber, a burner tube having an upstream end and a downstream end, a fuel orifice located adjacent the upstream end of the burner tube for introducing gaseous fuel into the burner tube, a burner tip having an outer diameter mounted on the downstream end of the burner tube adjacent a first opening in the furnace, so that combustion of the gaseous fuel takes place downstream of the burner tip, and at least one non-gaseous fuel gun, the at least one non-gaseous fuel gun having at least one fuel discharge orifice for combusting the non-gaseous fuel downstream of the discharge orifice, wherein the at least one non-gaseous fuel gun is radially positioned beyond the outer diameter of the burner tip so that a flame emanating from the combustion of the non-gaseous fuel is substantially aligned in parallel with a flame emanating from the combustion of the gaseous fuel.