Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) techniques were used to identify the local structural variations with SeO2 content for Li-ion conducting 0.5Li(2)O-0.5(YSeO2-(1-y)B2O3) (0.3 <= y <= 0.7) glasses. Based on the Se K-edge XAFS spectra, formation and growth of Se-O clusters were observed and also the valence state of Se cations in the glasses decreased with the increase of SeO2 content. The ratio of 3-fold coordinated boron (B-[3]) to 4-fold coordinated boron (B-[4]) in the glasses from the B Kedge NEXAFS spectra showed that incorporation of SeO2 in the network resulted in borate network depolymerization. The lithium ion conduction mechanism of Li2O-SeO2-B2O3 glasses was discussed in terms of the microstructural variation. (c) 2005 Elsevier B.V. All rights reserved.