A post-mix beverage dispenser comprising a fluid line (2) for supplying a base fluid, a dosing device (3) for introducing at least one liquid constituent into the base fluid so as to produce a mixed beverage, an outlet (4) for dispensing the mixed beverage, the dosing device (3) comprises an actuator (5) adapted to operate at least an airless dispensing pump (6) integral with or removable from the post-mix beverage dispenser for dispensing said liquid constituent in pre-established quantities, said pump (6) comprising a movable member (19) to be actuated by the actuator (5) and a pumping chamber (21) for containing said liquid constituent, the movable member (19) is associated to said pumping chamber (21) for causing the compression of the liquid constituent contained in the pumping chamber (21) and thereby the ejection of the liquid constituent from said pump (6).