A dispenser for the dosage of sanitizing and/or deodorant liquids, particularly for cisterns of toilet bowls, comprising: a container (2) for said liquid, which is adapted to float in the water of a cistern, at an upper level, and is provided, in a peripheral region (2a) thereof, with dosage means (5) connected to the outside through at least one opening (6); supporting means, having one end thereof anchored to fixed parts of said cistern and allowing said container to move from a floating position, which corresponds to said upper level and where said opening is directed upwards, to an active position, where said opening (6) is directed substantially downwards in order to allow to transfer a dose of said liquid when the water in said cistern is emptied.