The development of polymers with increasingly lower dielectric constants and losses has been the focus of several investigators. Accurate measurement of complex permittivity is needed for circuit design, minimization of cross talks, and characterization of signal-propagation speed. We have made PSF/PMMA blends and evaluated the dielectric parameters at 8.92 GHz frequency and at 350 C temperature. Dielectric measurements of blends show reduced dielectric constant than that of pure PSF. Decrease in dielectric constant in the blends may be attributed to enhanced free volume. Relaxation time for PSF/PMMA blends come out to be of the order of 10-13s. It comes out to be a bit higher in magnitude in the blends as compared to that of pure PSF. The increased relaxation time ( )values in blends may be due to the intermolecular interactions between PSF and PMMA molecules. Optical constants, absorption index 'K' and refractive index 'n' have also been evaluated.