De-convolution of impedance spectra is often ambiguous, mainly due to overlapped contributions, or when a prevailing interfacial contribution raises uncertainties about much smaller bulk contributions at higher frequencies. This can be avoided by performing impedance spectroscopy with a parallel external load resistance, which might exert selective decrease in interfacial contributions, with much smaller changes on high frequency contributions. By suitable selection of a parallel load resistance one obtained clearer interpretation for incompletely resolved high capacitance contributions, especially when the frequency range of the equipment does not reach sufficiently low frequencies. This method is discussed in detail and applied to de-convolution of impedance spectra of selected study cases. This includes ionic, or mixed conductors based on Yb(2)Ti(2)O(7), CGO and strontium titanate. One also provides guidelines for selection of suitable ranges of external resistors. (C) 2008 Elsevier Ltd. All rights reserved.