A unit (1, 1') for recovering and converting thermal energy from the exhaust gases of an internal combustion engine of a vehicle, said unit comprising: - a heat exchanger (2, 2') to be traversed by exhaust gases flowing along a by-pass path (5, 5') branching out from an exhaust gas main line of said internal combustion engine, and - valve means for controlling the flow of the exhaust gases through said path, said valve means being driven by an actuator device, - said by-pass path (5, 5') is a U-shaped path defined entirely by said heat exchanger (2, 2'), starting from an inlet section (6, 6') of said heat exchanger and ending at an outlet section of said heat exchanger, said inlet and outlet sections (7, 7') being located on a same side of the heat exchanger and both opening on an interface conduit portion interposed in said exhaust gas main line, said heat exchanger (2, 2') is arranged so that said U-shaped path is oriented transversely to the direction of the exhaust gas main line, in such a manner that the exhaust gases traversing the heat exchanger flow firstly in the transverse direction away from the exhaust gas main line and then back in the transverse direction towards the exhaust gas main line, - said valve means being arranged within said interface conduit portion, at a position axially intermediate between merging points of said inlet and outlet portions (6, 7) of the heat exchanger (5, 5'), - wherein said heat exchanger further comprises a heat exchange unit having an inlet orifice and an outlet orifice, said heat exchange unit being arranged to promote heat exchange between a fluid circulating therein and a fluid circulating in said path, wherein said unit is arranged to cooperate with an engine unit of a motor vehicle comprising said internal combustion engine, wherein the fluid circulating inside said heat exchange unit is cooling water of said internal combustion engine, characterized in that said outlet orifice of said heat exchange unit is connected to a cabin heater, and in that the inlet orifice of said heat exchange unit is connected to a heat exchanger for EGR operatively connected to said internal combustion engine. - a heat exchanger (2, 2') to be traversed by exhaust gases flowing along a by-pass path (5, 5') branching out from an exhaust gas main line of said internal combustion engine, and - valve means for controlling the flow of the exhaust gases through said path, said valve means being driven by an actuator device, - said by-pass path (5, 5') is a U-shaped path defined entirely by said heat exchanger (2, 2'), starting from an inlet section (6, 6') of said heat exchanger and ending at an outlet section of said heat exchanger, said inlet and outlet sections (7, 7') being located on a same side of the heat exchanger and both opening on an interface conduit portion interposed in said exhaust gas main line, said heat exchanger (2, 2') is arranged so that said U-shaped path is oriented transversely to the direction of the exhaust gas main line, in such a manner that the exhaust gases traversing the heat exchanger flow firstly in the transverse direction away from the exhaust gas main line and then back in the transverse direction towards the exhaust gas main line, - said valve means being arranged within said interface conduit portion, at a position axially intermediate between merging points of said inlet and outlet portions (6, 7) of the heat exchanger (5, 5'), - wherein said heat exchanger further comprises a heat exchange unit having an inlet orifice and an outlet orifice, said heat exchange unit being arranged to promote heat exchange between a fluid circulating therein and a fluid circulating in said path,