The present invention relates to a drive mechanism for a drug delivery device for dispensing of a dose of a medicament, and to a respective drug delivery device, wherein the drive mechanism comprises: —an elongated housing (30) extending in an axial direction (1, 2), —a piston rod (80) to operably engage with a piston (16) of a cartridge (14) to displace the piston (16) in axial distal direction (1), —a drive sleeve (60) extending in axial direction (1, 2) and being rotatably supported in the housing (30), —a dose setting member (40) rotatably supported on a side wall portion (31) of the housing (30) and being rotatable with respect to an axis (41) extending in radial direction (r), —wherein the drive sleeve (60) is operably releasable from the piston rod (80) and rotatably engageable with the dose setting member (40) for setting of the dose.