Cyclic voltammetry, electrochemical impedance spectroscopy, and computational chemistry methods have been applied for investigation of electrochemically polished Bi(111) electrode in 1-butyl-4-methylpyridinium tetrafluoroborate (BMPyBF4) ionic liquid. The region of ideal polarizability, series resistance and capacitance, limiting high-frequency and low-frequency capacitances have been obtained and compared with those established for 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)). Differently from Bi(111)vertical bar EMImBF(4) interface, noticeably more expressed influence of the mass transfer limited step on the electrical double layer formation kinetics has been demonstrated and explained by the higher viscosity of BMPyBF4. Possible reasons of the lower values of series capacitance for Bi(111)vertical bar BMPyBF4 compared with Bi(111)vertical bar EMImBF(4) interface has been examined on the basis of modern theoretical models. (C) 2012 Elsevier B.V. All rights reserved.