The electronic bands of aLiB3O5(LBO) crystal with excellent nonlinear optical properties have been studied using the scattered-wave method in embedded-cluster model. Calculations were carried out for a [B3O7]5−cluster, as this anionic group is the crystal basic structural unit. The interpretation of experimental photoemission spectra is based on electronic structure cluster calculations. From calculation performed, it follows that the contribution of trigonal and tetrahedral boron-oxygen groups dominates in the electronic structure of LBO, the contribution of 2p-boron states is immaterial.