The vacuum-ultraviolet (VUV) spectroscopic properties of undoped and Tb3+-doped borates Ba(3)Ln(BO3)(3) (Ln = Lu and Gd) with different crystal structures were investigated by using synchrotron radiation. Ba3Lu(BO3)(3) (BLB) crystallizes in a hexagonal structure, whereas Ba3Gd(BO3)(3) (BGB) crystallizes in a trigonal structure. The maximum host absorption for BLB and BGB was found to locate at similar to 179 and similar to 195 nm, respectively. Upon host excitation, BLB exhibits an intrinsic broad UV emission centered at 339 nm, which is attributed to the recombination of self-trapped excitons that may presumably be associated with band-gap excitations or molecular transitions within the BO33- group. In contrast to BLB, no broad emission but line emission ascribed to a Gd3+ P-6(J)-S-8(7/2) 712 transition was observed in the emission spectrum of BGB. Upon doping of Tb3+ ions into the hosts of BLB and BGB, an efficient energy transfer from the host excitations to Tb3+ via host/Gd3+ emission was observed, showing that host sensitization of Tb3+ occurs in these rare-earth borates.