Colorless single crystals of LiSb(OH)(6), SrSn(OH)(6), and BaSn(OH)(6), which are useful as precursors for the synthesis of LiSbO3, SrSnO3, and BaSnO3, were synthesized by a low-temperature hydrothermal method using a Teflon-lined autoclave at 380 K. The crystal structures were determined by single-crystal X-ray diffraction measurements. LiSb(OH)(6) crystallizes in the trigonal space group P (3) over bar 1m with a = 5.3812(3)A, c = 9.8195(7)A, V = 246.25(3)A(3), Z = 2. In this layered structure, [Li2Sb(OH)(6)](+) and [Sb(OH)(6)](-) layers are alternately stacked along the c-direction. The [Li2Sb(OH)(6)](+) layer can be regarded as a cation-ordered CdCl2 layer. The [Sb(OH)(6))](+) layer is built up from isolated [Sb(OH)(6)](-) octahedra, which are linked to each other via hydrogen bonding within the layer. BaSn(OH)(6) and SrSn(OH)(6) crystallize with monoclinic P2(1)/n space group symmetry. The monoclinic structure possesses a CsCI-type packing of Ba2+/Sr2+ cations and [Sn(OH)(6)](2-) anions. The [Sn(OH)(6)](2-) polyhedra are connected to each other through hydrogen bonding to form a three-dimensional framework. The factors that favor these hitherto unknown crystal structures are discussed using a structure map that compares various M(OH)(3) and M'M ''(OH)(6) compounds.