Abstract: The present invention relates to a piston intended for a hydraulic radial piston motor and being of the type comprising an outer cam ring having an undulated inner cam surface, an inner cylinder block which is rotatable relative to the cam ring and has radially outwardly directed cylinders, a plurality of such pistons which move in said cylinders and cam rolls which rollingly run against the cam surface and are slidingly arranged against the respective pistons. The piston has an essentially cylindrical circumferential surface, an inner end surface and an opposite outer end surface, which is adapted to be slidingly arranged against the cam roll and therefore is formed with a groove-like recess, which in cross-section is essentially part-cylindrical, and with two lateral portions which extend around and partly surround the circumferential surface of the cam roll and via which reaction forces in the tangential direction of the cylinder block are transmitted between the cam roll and the cylinder block.