A model for predicting leveling during electrodeposition in the presence of an inhibiting additive is presented. Based on a diffusion-adsorption mechanism, the model assumes that the additive is consumed at the cathode by electroreduction. Using the approximation of a flat, stagnant diffusion layer, leveling during metal electrodeposition into triangular and semicircular grooves is simulated. The variation of the leveling agent concentration along the groove profile is determined by solving a concentration field problem with a boundary element method, and the advancement of the groove profile is simulated with a flexible moving-boundary algorithm. Leveling performance depends on three dimensionless groups characterizing leveling-agent reduction, metal-ion reduction, and the geometrical ratio of the diffusion layer thickness to the groove depth.