Positioning and extraction assembly for a machine for the preparation of a beverage using capsules having a body provided with a protruding flange, the assembly comprising: first and second portions (17, 18), at least one of which is movable with respect to the other one between an open position in which a capsule can be introduced therebetween, and a closed position in which said capsule is enclosed in an infusion chamber for the preparation of a beverage; the assembly comprising, between said first and second portions (17, 18), means for positioning the capsule, including two opposite, rotatable, gates, with which respective resilient opposing means are associated, which tend to keep them in a working position in which they are capable of forming, at least in part, guides or seats for receiving and retaining in an intermediate waiting position a capsule introduced into the assembly, said capsule being able to open said gates and pass beyond them, when said portions (17, 18) of the assembly pass from the open position to the closed position, said gates being capable of preventing a return of the capsule to said intermediate position when said portions (17, 18) of the assembly return to the open position; the assembly being characterized in that the resilient means associated with each of said gates comprise a flexion spring including an essentially L- or V-shaped resilient strip, with an outer anchoring portion fixed to one of said portions (17, 18) of the assembly in an orientation which is at least approximately parallel to said direction of movement (A-A), and an inner opposing portion which extends towards said direction of movement (A-A) and bears against the associated gate on the side opposite the corresponding guide or seat for the capsule. first and second portions (17, 18), at least one of which is movable with respect to the other one between an open position in which a capsule can be introduced therebetween, and a closed position in which said capsule is enclosed in an infusion chamber for the preparation of a beverage; the assembly comprising, between said first and second portions (17, 18), means for positioning the capsule, including two opposite, rotatable, gates, with which respective resilient opposing means are associated, which tend to keep them in a working position in which they are capable of forming, at least in part, guides or seats for receiving and retaining in an intermediate waiting position a capsule introduced into the assembly, said capsule being able to open said gates and pass beyond them, when said portions (17, 18) of the assembly pass from the open position to the closed position, said gates being capable of preventing a return of the capsule to said intermediate position when said portions (17, 18) of the assembly return to the open position; the assembly being characterized in that the resilient means associated with each of said gates comprise a flexion spring including an essentially L- or V-shaped resilient strip, with an outer anchoring portion fixed to one of said portions (17, 18) of the assembly in an orientation which is at least approximately parallel to said direction of movement (A-A), and an inner opposing portion which extends towards said direction of movement (A-A) and bears against the associated gate on the side opposite the corresponding guide or seat for the capsule.