The effect of inclination of electrochemical cell with plane-parallel electrodes in the gravitational field on the limiting current of electrochemical reaction is theoretically analyzed by the example of iodine-iodide system. The quantitative dependences of the limiting current on the angle a between the electrodes and the horizontal are obtained. It is shown that this effect is associated with the variation in the distributions of solution concentration and hydrodynamic velocity with a. It is found that the ratio between the electrode's length and the interelectrode distance is of great importance.