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 P3̅1m with a = 5.3812(3)A, c = 9.8195(7)A, V = 246.25(3)A³, 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 P2₁/n space group symmetry. The monoclinic structure possesses a CsCl-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.