The　electronic　structures　of　three　wurtzite　type　isostructural　compounds　LiBSe2　(B=Al,　Ga,　In)　are　studied　by　the　density　functional　theory　(DFT).　The　results　reveal　that　the　presence　of　Li　cations　has　direct　influence　on　neither　the　band　gaps　(Eg)　nor　the　bonding　levels,　but　plays　an　important　role　in　the　stabilization　of　the　structures.　The　band　structures　and　densities　of　states　(DOS)　are　analyzed　in　detail,　and　the　band　gaps　of　LiBSe2　adhere　to　the　following　trend　Eg(LiAlSe2)>Eg(LiGaSe2)>Eg(LiInSe2),　which　is　in　agreement　with　the　decrease　of　the　bond　energy　of　the　corresponding　Se　4p-B　s　antibonding　orbitals.　The　role　of　the　active　s　electrons　of　B　element　on　the　band　gaps　is　also　discussed.　Finally,　the　optical　properties　are　predicted,　and　the　results　would　be　a　guide　to　understand　the　experiments.　©　2008　Elsevier　Inc.　All　rights　reserved.