Electric circuit networks based on lumped components and distributed impedance elements are considered in the analysis of impedance spectroscopy data of nano-structured materials. A procedure based on transformation among degenerate networks is used as synthesis of linear, passive, one-port electric schemes and non-distinguishable distributed elements due to the noise level in observed data. Experimental results obtained on nitrogen doped ultra-nanocrystalline-diamond thin films are used to illustrate this process. (C) 2011 Elsevier B.V. All rights reserved.