Abstract The Mayadas-Shatzkes and the Wissmann-Wedler models for the electrical conductivity of thin polycrystalline metal films are discussed. It can be shown that the Wissmann-Wedler equation is an approximation to the Mayadas-Shatzkes equation. This approximation is valid when the film is not too thick and the grain boundary influence on the electrical resistivity is not too strong. A correlation between the parameters of the two models is derived. Conditions for the validity of Matthiessen's rule for the description of the grain boundary influence are given.