The electron paramagnetic resonance spectra of layered perovskite Rb 2 ZnF 4 and Rb 2 CdF 4 doped with Fe 3+ are studied by means of a 252×252 complete energy matrix for a 3d 5 configuration ion in a tetragonal ligand-field. The local structure parameters R ⊥ and R ∥ for Rb 2 ZnF 4 :Fe 3+ and Rb 2 CdF 4 :Fe 3+ systems are determined. The calculations show that the local lattice of the Rb 2 ZnF 4 :Fe 3+ and Rb 2 CdF 4 :Fe 3+ systems display a compression distortion relative to the regular octahedron. Besides, the value of R ⊥ in Rb 2 ZnF 4 and Rb 2 CdF 4 crystals is, respectively, larger than that in Rb 2 ZnF 4 :Fe 3+ and Rb 2 CdF 4 :Fe 3+ systems. This may be ascribed to the fact that Fe 3+ ions have the smaller ionic radius and larger charge in comparison to Zn 2+ and Cd 2+ ions. In the end, the relative curves of 104b20 vs. ΔR (ΔR=R ⊥ −R ∥ ) for these two systems are plotted which satisfy an approximately linear relation.