Abstract-Luebbers' and Maliuzhinets' solutions for diffraction by a lossy wedge are compared in order to model the urban propagation channel. Derivation, validity criteria and accuracy of impedance boundary conditions (IBCs)-as a main approximation embedded in the Maliuzhinets' solution-are discussed. A modified (a slightly improved) Luebbers diffraction coefficient is proposed. The Uniform Theory of Diffraction (UTD) Maliuzhinets diffraction coefficient is given in a structured form that might facilitate its use. Detailed numerical comparisons of the above-mentioned solutions with methodof-moments solutions using either exact boundary conditions or IBCs are done for canonical configurations.