A cup dispenser for a beverage vending machine; the cup dispenser comprises at least a cup containment and release assembly with a longitudinal axis and comprising a containment portion, which defines a guide channel coaxial with the longitudinal axis and adapted to contain a stack of cups; and a release portion, which is arranged below the containment portion and is configured to support the stack of cups and single out individual cups from the bottom of the stack of cups; the containment portion comprises a number of containment members laterally delimiting the guide channel; the containment members are mounted to be radially movable to modify a cross section of the guide channel; the containment members are radially moveable between a maximum opening position, in which the guide channel is so sized as to contain larger cups, and a minimum opening position, in which the guide channel is so sized as to contain smaller cups; the cup containment and release assembly comprises an adjustment device configured to simultaneously move all the containment members between the maximum and minimum opening positions; the adjustment device comprises a first adjustment ring mounted to rotate about the longitudinal axis, and a number of first lever mechanisms, each of which kinematically connects the first adjustment ring and a corresponding containment member to move the containment member between the maximum and minimum opening positions in response to a rotation of the first adjustment ring about the longitudinal axis; the release portion comprises a release device with a number of release members; in order to radially adjust the position of the release members, the adjustment device comprises a second adjustment ring and a number of second lever mechanisms, which are functionally equivalent to the first adjustment ring and, respectively, to the first lever mechanisms and are arranged at the release members; the first adjustment ring and the second adjustment ring are mutually angularly coupled so that a radial movement of the containment members corresponds to the same radial movement of the release members. the containment portion comprises a number of containment members laterally delimiting the guide channel; the containment members are mounted to be radially movable to modify a cross section of the guide channel; the containment members are radially moveable between a maximum opening position, in which the guide channel is so sized as to contain larger cups, and a minimum opening position, in which the guide channel is so sized as to contain smaller cups; the cup containment and release assembly comprises an adjustment device configured to simultaneously move all the containment members between the maximum and minimum opening positions; the adjustment device comprises a first adjustment ring mounted to rotate about the longitudinal axis, and a number of first lever mechanisms, each of which kinematically connects the first adjustment ring and a corresponding containment member to move the containment member between the maximum and minimum opening positions in response to a rotation of the first adjustment ring about the longitudinal axis; the release portion comprises a release device with a number of release members; in order to radially adjust the position of the release members, the adjustment device comprises a second adjustment ring and a number of second lever mechanisms, which are functionally equivalent to the first adjustment ring and, respectively, to the first lever mechanisms and are arranged at the release members; the first adjustment ring and the second adjustment ring are mutually angularly coupled so that a radial movement of the containment members corresponds to the same radial movement of the release members.