This paper deals with impedance measurement of gas sensors with active layers prepared by pulsed laser deposition (PLD) technology. The deposition was carried out from tin dioxide (SnO 2 ) and tin acetylacetonate (SnAcAc)-based targets by KrF (248nm) excimer laser. The main interest was focused to following problems: measurements of real and imaginary part of complex impedance for frequencies ranging from 100Hz to 10MHz (Nyquist diagram), comparison of layers based on both organic and inorganic materials, the influence of dopants (NiO, Fe 2 O 3 , FeAcAc) and catalyst (Pd). As a result of analysis of Nyquist diagrams an alternative phase-angle sensitivity S p a (based on phase shift) to atmosphere containing reducing gas in ''pure'' synthetic air was proposed.