A discrepancy has been observed between the experimental behavior of electrical resistivity and temperature coefficient of resistivity as a function of film thickness in thin single‐crystal silver films when compared with geometrical size effect theory. The discrepancy has been attributed to the observed change in the microstructure of the films as shown by the transmission electron microscopy study and to the effect of lattice as well as electron energy quantization on electrical conduction. The study calls for an exact calculation of the role of quantization in structurally perfect thin films.