Relationships among Xe-129 NMR chemical shift, Xe sorption properties, and density have been investigated for poly(2,6-dimethyl-1,4-phenylene oxide) / polystyrene miscible blend system in order to evaluate the variation of microvoids by blending. Xe sorption isotherms of all samples have been explained successfully on the basis of the dual-mode sorption model. Xe sorption properties and densities of blended samples have indicated the reduction of microvoids by blending. Xe-129 NMR chemical shifts of Xe-129 sorbed in each sample have shown a non-linear low-field shift with increasing total amount of Xe sorption. Estimation of the microvoids by Xe-129 NMR spectroscopy has been consistent with the results of density and Xe sorption measurements.