Reduction of RCS of military targets is important issue and can be regarded as part of passive ECM (Electronic Counter Measure). Reduction of RCS is basically made by multilayer coating the surface of the target by lossy dielectrics. In this case ' boundary condition which is satisfied on the surface of target can be modelled by IBC (Impedance Boundary Condition). We propose the method that determines the surface impedance value of the cylinder satisfying reduced bistatic RCS. We also applied the proposed method to minimise the mono-static RCS of the impedance cylinder. Minimised mono-static RCS was compared to those of perfectly electrical conductor (PEC) cylinder and good reduction values were observed over a wide frequency range and angle.