We studied structure of SiO2-/SiC interfaces grown by thermal oxidization using low energy positron beams. From the positron lifetime measurements, typical two lifetime components related to amorphous network and large open spaces are observed in SiO2, while only bulk lifetime in SiC. The lifetime of positrons near the interface is similar to that of SiO2 amorphous network and no lifetime components related to large open spaces are detected. From the Doppler broadening measurements, the momentum distribution, probably related to oxygen valence electrons, is enhanced near the interface. The above results imply that the interface region has less open spaces than SiO2 involving many oxygen dangling bonds. (c) 2005 Elsevier B.V. All rights reserved.