During operation of gas-evolving electrodes, a fraction of the electrode surface is covered with adhering gas bubbles, which are known to exert substantial effect on mass and heat transfer, on overpotential, on limiting current density and on ohmic resistance. For this reason, many investigations were conducted to obtain experimental data of the fractional bubble coverage (or fractional shielding) in stagnant liquids. However, very little attention has been paid to the behaviour in liquid flow, although the majority of industrial electrochemical reactors are operated with flowing electrolyte liquids. The paper presents a theoretical analysis and experimental results of the effect of liquid velocity on the bubble coverage.