Colorless crystals of the barium rare earth hydrogarnets Ba3[RE(OH)6]2 (RE = Sc, Y, Ho–Lu) were synthesized under hydroflux conditions with KOH at about T = 200 °C starting from the respective RE2O3 and Ba (NO3)2. Single-crystal X-ray diffraction analysis on these distorted rhombic dodecahedra revealed the cubic space group Ia$‾{3}$d (no. 230). The crystal structures of the hydrogarnets Ba3[RE(OH)6]2 are discussed and compared with those of other hydrogarnets. The occurrence of additional reflections, which do not fulfill the reflection conditions of Ia$‾{3}$d, is analyzed and described by Renninger or λ/2 effects. A correlation is established between the space group adopted by a hydrogarnet and characteristic interatomic distances. In addition, single-crystal structure data of the strontium indium hydrogarnet Sr3[In(OH)6]2 are provided.