Speed control device for a hand-portable pneumatic power tool which includes a housing with a pressure air inlet, an output spindle, an air turbine with a turbine wheel drivingly connected to the output spindle, wherein a plurality of nozzles are arranged for directing motive air onto the turbine wheel, and a speed control device, wherein the speed control device includes a valve unit for controlling pressure air flow through the nozzles in response to a speed responsive parameter, wherein - said plurality of nozzles is divided into separate nozzle groups (12, 13, 14) having individual air feed through individual air feed passages, - there are n (n is an integer n > 1) nozzle groups (12, 13, 14) and that the valve unit is capable of being actuated into n states for controlling air feed to said n nozzle groups, whereby for each subsequent state, x (1 ≤ x ≤ n, x is an integer) air feed passages (15, 16, 17) are connected to the pressure air inlet such that nozzle groups 1 → x are fed with air, - the valve unit includes a valve element which has a cylindrical skirt portion with one or more radial apertures which are arranged to co-operate with a number (n) of axially differently oriented radial openings (25', 26', 27') in a valve housing, wherein the valve element is sealingly axially movable, said radial openings being respectively connected to said air feed passages, and - wherein the radial apertures and possibly also the radial openings (25', 26', 27'), are positioned evenly distributed around the circumferences of associated valve parts in order to obtain force balance in radial directions of said parts, and characterized in - that said speed responsive parameter is a speed responsive control pressure related to an air flow downstream of the turbine wheel and the valve element is coupled to a piston means which in turn is arranged to be actuated by said speed responsive control pressure, - that said power tool comprises a channel for transmitting said speed responsive control pressure from downstream of the turbine wheel for the action of the pressure on a first piston area of the piston means, and means for transmitting the inlet air pressure for the action of the pressure on a second piston area (a) of the piston means for balancing the piston means, thereby balancing the valve element between said pressures. - said plurality of nozzles is divided into separate nozzle groups (12, 13, 14) having individual air feed through individual air feed passages, - there are n (n is an integer n > 1) nozzle groups (12, 13, 14) and that the valve unit is capable of being actuated into n states for controlling air feed to said n nozzle groups, whereby for each subsequent state, x (1 ≤ x ≤ n, x is an integer) air feed passages (15, 16, 17) are connected to the pressure air inlet such that nozzle groups 1 → x are fed with air, - the valve unit includes a valve element which has a cylindrical skirt portion with one or more radial apertures which are arranged to co-operate with a number (n) of axially differently oriented radial openings (25', 26', 27') in a valve housing, wherein the valve element is sealingly axially movable, said radial openings being respectively connected to said air feed passages, and - wherein the radial apertures and possibly also the radial openings (25', 26', 27'), are positioned evenly distributed around the circumferences of associated valve parts in order to obtain force balance in radial directions of said parts, and characterized in - that said speed responsive parameter is a speed responsive control pressure related to an air flow downstream of the turbine wheel and the valve element is coupled to a piston means which in turn is arranged to be actuated by said speed responsive control pressure, - that said power tool comprises a channel for transmitting said speed responsive control pressure from downstream of the turbine wheel for the action of the pressure on a first piston area of the piston means, and means for transmitting the inlet air pressure for the action of the pressure on a second piston area (a) of the piston means for balancing the piston means, thereby balancing the valve element between said pressures.