The electric Ohm resistivity rho of electroless Cu layers on glass substrates as a function of deposition thickness is studied. Deviations up to 200 times from the standard resistivity (rho(infinity) (Cu) = 1.7 muOmega cm) below 100 nm deposition thickness reported in other papers are confirmed. A comparative analysis shows different reasons for the higher resistivity of thin electroless layers and evaporated ones. A diagram with variables taken from the so-called Fuchs theory correct for thin evaporated metallic layers quantitatively illustrates conductance differences of electroless and evaporated layers. It is supposed that at electroless layers the isolated areas of deposition as well as the strong branching of the conducting circuits play major role. Calculation of the relative resistivity rho/rho(infinity) of a real sample show good agreement with the proposed model. (C) 2003 Kluwer Academic Publishers.