A hydraulic damper , in particular a motor vehicle suspension damper, comprising a main tube extending along an axis (A) and filed with working fluid, a main piston assembly disposed slidably inside the main tube , attached to a piston rod led outside the hydraulic damper through a sealed piston rod guide , dividing the main tube into a rebound chamber and a compression chamber , and provided with rebound and compression valve assemblies to control the flow of working fluid passing between the rebound chamber and the compression chamber , characterized in that said piston rod is provided with an annular chamber in which a slidable partition is disposed dividing this chamber into a magnetorheological chamber , proximal to the main piston assembly and filled with magnetorheological fluid, and a compensation chamber , distal to the main piston assembly and filed with gas, wherein said hydraulic damper further comprises a secondary piston assembly slidably disposed inside said magnetorheological chamber , attached to a secondary piston rod sealingly and slidably guided through the main piston assembly and axially fixed with respect to the main tube , dividing said magnetorheological chamber into a magnetorheological compression chamber , distal to the main piston assembly , and a magnetorheological rebound chamber , proximal to the main piston assembly , wherein said secondary piston assembly is provided with a flow channel and at least one electromagnet coil for variably generating a magnetic flux modifying shear resistance of magnetorheological fluid to control the flow of magnetorheological fluid passing through said flow channel between said magnetorheological rebound chamber and said magnetorheological compression chamber , wherein said at least one electromagnet coil is connected with a control cable passing through said secondary piston rod and led outside the hydraulic damper , wherein said piston rod comprises an extender fixed to the main piston assembly , a cylindrical body fixed to said extender and defining said magnetorheological chamber and said compensation chamber , and a mounting projection fixed to said cylindrical body at its end distal to the main piston assembly . a secondary piston assembly slidably disposed inside said magnetorheological chamber , attached to a secondary piston rod sealingly and slidably guided through the main piston assembly and axially fixed with respect to the main tube , dividing said magnetorheological chamber into a magnetorheological compression chamber , distal to the main piston assembly , and a magnetorheological rebound chamber , proximal to the main piston assembly , wherein said secondary piston assembly is provided with a flow channel and at least one electromagnet coil for variably generating a magnetic flux modifying shear resistance of magnetorheological fluid to control the flow of magnetorheological fluid passing through said flow channel between said magnetorheological rebound chamber and said magnetorheological compression chamber , wherein said at least one electromagnet coil is connected with a control cable passing through said secondary piston rod and led outside the hydraulic damper , wherein said piston rod comprises an extender fixed to the main piston assembly , a cylindrical body fixed to said extender and defining said magnetorheological chamber and said compensation chamber , and a mounting projection fixed to said cylindrical body at its end distal to the main piston assembly . <EOS>