We investigate the effect of bulk velocity of the solar wind on the propagation characteristics of ion-cyclotron waves (ICWs). Our model is based on the kinetic theory. We solve the Vlasov equation for O VI ions and obtain the dispersion relation of ICWs. Refractive index of the medium for a streaming bi-Maxwellian velocity distribution proved to be higher than that of the bi-Maxwellian velocity distribution. The bulk velocity of the solar polar coronal holes' plasma increases the value of the refractive index by a factor of 1.5 (3) when the residual contribution is included (neglected). The ratio of the refractive index of interplume lanes to the plume lanes at the coronal base is also higher than we found for the bi-Maxwellian velocity distribution, i.e. k(interplume)/k(plume) = 2.5. (C) 2012 Elsevier B.V. All rights reserved.