A portable power tool wherein the housing contains a pump, a tank for a supply of oil for the pump, an electric motor for the pump and one or more hydraulic motors which receive pressurized oil from the pump and impart movements to a rotary and/or reciprocable tool, such as a rock drill or chisel. The motor which imparts reciprocatory movements to the tool is a cylinder and piston unit whose piston is rigid with a piston rod serving to strike against the tool whenever the piston performs a forward stroke. A valve assembly having a motor-driven rotary spool controls the flow of pressurized fluid to and the outflow of spent fluid from the cylinder. A spring brakes the rearward movements of the piston, and a bladder type accumulator is connected with the outlet of the pump. The tank is cooled by currents of air which are induced by a blower on the output shaft of the electric motor and which cool the electric motor before they reach cooling fins provided at the outer side of the tank.