Current-voltage characteristics of ion transfer across the ITIES was theoretically studied, concentration polarization into account through the Nernst-Planck equation in the diffusion boundary layers. In the inner layer transport was modelled using either Butler-Volmer or Nernst-Planck equations. Potential distribution across the ideally polarizable ITIES was calculated from the Poisson-Bolzman equation. The current-voltage curves were of the Butler-Volmer type, but no distinction between the two approaches inside the inner layer could be seen because the permeability of the entire system was determined by the diffusion boundary layers.