Compressor for a refrigerating plant comprising: at least two cylinders; at least two pistons, which slides alternately inside the cylinders; at least two heads provided with two suctions chambers, connected to a suction line of the plant and to the cylinders to supply the at least two cylinders with a refrigerating fluid, and with a first suction valve, configured to regulate the refrigerating fluid flow rate to a first cylinder; the first suction valve being movable between a first position, wherein is defined a first flow area which allows the suction of a first flow rate of refrigerating fluid, and a second position wherein is defined a second flow area smaller than the first flow area which allows the suction of a second flow rate of refrigerating fluid lower than the first flow rate; wherein a first suction chamber is divided into two portions by a partition provided with an opening through which the refrigerating fluid flows; wherein the first suction valve comprises a shutter configured to engage the opening of the first suction chamber in the second position; the shutter and the opening being shaped so as to define the first flow area in the first position and the second flow area in the second position; and wherein there is at least a second cylinder; at least a second piston, which slides alternately inside the second cylinder; a second head provided with a second suction chamber, connected to the suction line of the plant and to the second cylinder to supply the second cylinder with a refrigerating fluid, and with a second suction valve, configured to regulate the refrigerating fluid flow rate to the second cylinder; the second suction valve being movable between a third position, wherein is defined a third flow area which allows the suction of a third flow rate of refrigerating fluid, and a fourth position wherein the third flow area is occluded. at least two cylinders; at least two pistons, which slides alternately inside the cylinders; at least two heads provided with two suctions chambers, connected to a suction line of the plant and to the cylinders to supply the at least two cylinders with a refrigerating fluid, and with a first suction valve, configured to regulate the refrigerating fluid flow rate to a first cylinder; the first suction valve being movable between a first position, wherein is defined a first flow area which allows the suction of a first flow rate of refrigerating fluid, and a second position wherein is defined a second flow area smaller than the first flow area which allows the suction of a second flow rate of refrigerating fluid lower than the first flow rate; wherein a first suction chamber is divided into two portions by a partition provided with an opening through which the refrigerating fluid flows; wherein the first suction valve comprises a shutter configured to engage the opening of the first suction chamber in the second position; the shutter and the opening being shaped so as to define the first flow area in the first position and the second flow area in the second position; and wherein there is at least a second cylinder; at least a second piston, which slides alternately inside the second cylinder; a second head provided with a second suction chamber, connected to the suction line of the plant and to the second cylinder to supply the second cylinder with a refrigerating fluid, and with a second suction valve, configured to regulate the refrigerating fluid flow rate to the second cylinder; the second suction valve being movable between a third position, wherein is defined a third flow area which allows the suction of a third flow rate of refrigerating fluid, and a fourth position wherein the third flow area is occluded.