Abstract: Method of physical optics is used to calculate the backscattering cross section of nonorthogonal dihedral corner reflectors coated by radar absorbing materials (RAM), illuminated in an arbitrary direction. Singly, doubly, and triply reflected contributions are considered. The results are then compared with those applying the method of moment, which shows that the trend of backscattering cross section of the dihedral corner reflector can be accurately predicted with this method.