A wet electrostatic precipitator (1) includes an inlet (2) for receiving a gas (4) containing a pollutant, and an outlet (6) for discharging therefrom the gas (8) from which said pollutant has been at least partially removed. Nozzles (24) are operative for purposes of spraying liquid onto at least one first vertical collecting surface (30) of at least one collecting electrode (18). A liquid distributor (42) is provided for purposes of pouring liquid onto at least one second vertical collecting surface (44), said at least one second vertical collecting surface (44) being located on a further collecting electrode (36), with said further collecting electrode (36) being located downstream of said at least one collecting electrode (18). The nozzles (24) are located upstream of the liquid distributor (42), as viewed with reference to the direction of flow of the gas. In a method of cleaning the collecting electrodes (18, 36) an upstream electrode (18) is sprayed with liquid while liquid is poured onto a downstream collecting electrode (36).