In the process engineering industry tanks with large volumes from 250 to 1000 m(3) are often required, which are flowed through by large gas volume flows up to 150 000 m(3) h(-1). The flow leads to a mean flow velocity from 0.347 -1.0 m s(-1). The inflow and outflow of the gas have to be done by one or two inlet and outlet pipes with diameter sizes of 1.20 to 2.0 m. Nevertheless, with respect to the chemical or catalytic reaction, a constant flow velocity is required in the tank. This paper shows how gas distribution plates for crosswise flow tanks or catalysts with a differential cross section distribution can be calculated and designed for the flow-through area, which nearly ensure a constant flow velocity without an increase of the flow resistance.