Silver-needle shaped crystals of KLa2Sb3S 9 from K2Sx flux and KSm2Sb 3Se8 from NaCl/KCl flux reactions were obtained and their crystal structures were determined by the single crystal X-ray diffraction method. KLa2Sb3S9 crystallizes in the orthorhombic noncentrosymmetric space group P21212 1 (No. 19) with a unit cell of a = 4.220(3) Å, b = 24.145(2) Å, c = 14.757(5) Å and Z = 4. KSm2Sb3Se 8 crystallizes in the orthorhombic space group Pnma (No.62) with a unit cell of a = 16.719(3) Å, b = 4.1236(8) Å, c = 22.151(4) Å and Z = 4. Both structures have three-dimensional tunnel frameworks filled with K+ ions. KSm2Sb3Se8 is an ordered version of ALn1 ± xBi4 ± xS 8, and it is made up of NaCl-type and Gd2S 3-type fragments. KLa2Sb3S9 also contains building fragments similar to those of KSm2Sb 3Se8, however, there are chalcogen-chalcogen bonds in the Gd2S3-type fragment. The formula of KLa2Sb 3S9 can be described as (K+)(La 3+)2(Sb3+)3(S2-) 7(S2 2-).