This paper presents a simple analytical method to describe both effects of linear transmission line losses and, for the first time, frequency dispersion on photonic band-gap (PBG) propagation parameters. Applied to a coplanar waveguide PBG structure, this approach points out the attenuation difference between the two frequently used electrical models : one with fully distributed parameters and one with semi distributed parameters. Moreover, a comparison of the same PBG design with three technologies of transmission lines (CPW, MS and Fin-line) gives very interesting results on the Bragg frequency value and the PBG attenuation.