X-ray diffraction studies of four alkoxy cyanobiphenyls (alkyl = nonyl, decyl, undecyl and dodecyl) have been undertaken to determine orientational order parameters, layer thickness, packing fraction and coefficients of HJL type potential. All these values show some odd-even effect with the number of chain carbon atoms. Powder X-ray patterns from these compounds in solid phase have also been indexed satisfactorily. Orientational order parameters have been fitted to those calculated from McMillan's theory by varying the parameters a and σ.