A cup dispenser for a beverage vending machine; the cup dispenser comprises at least a cup containment and release assembly with a longitudinal axis (B) and comprising a containment portion , which defines a guide channel coaxial with the longitudinal axis (B) 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 (B), 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 (B); 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 (B), 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 (B); 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 . <EOS>