Granular polysilicon is fed into a screening plant, divided into two or more fractions by means of one or more screen surfaces, and thereby classified and dedusted wherein a throwing motion of the granular polysilicon in the screening plant removes adhering dust particles from the granular polysilicon, the removed dust particles are taken off from the screening plant by means of a gas flow supplied to the screening plant, and the screening plant is of gas-tight design and supply and takeoff of the gas flow are effected such that the screening plant is at a positive pressure compared to the surroundings.