It is shown that even the high frequency part of an impedance spectrum of barrier coatings cannot be explained solely by a constant phase element. A continuous time random walk mechanism is proposed to explain the 'hanging' phase angle course in the medium frequency range of the barrier coatings under test. The assumed dielectric relaxation mechanism, based on dipole relaxation triggered by migrating defects is able to explain the observed capacity dispersion. The two-step random walk model, originally developed for the interpretation of experimental data obtained in the time domain, is evaluated in the frequency domain numerically. The approximation of the resulting impedance transfer function enables the application of this model in an EIS analysis program. (c) 2005 Elsevier Ltd. All rights reserved.