Abstract: An arrangement and a rotor for screening of pulp is disclosed that is suitable for the screening of chemical and mechanical pulps, i.e. fiber suspensions of the wood processing industry. A feature of the arrangement and rotor is that inside the rotor (16) there is arranged at least one dilution liquid chamber (24′, 24″, 24′″) restricted by a surface of the rotor (16), which surface is provided with means for connecting said at least one chamber (24′, 24″, 24′″) with the screening space defined between the rotor and the screen drum in such a way that dilution liquid from said at least one chamber (24′, 24″, 24′″) is brought into the screening space at a distance of at least 20 mm from the inner surface of the screen drum (14).