[en] Methods of X-ray diffraction and phase analyses were used to study compounds of Ca₂LnTaO₆ composition, where Ln=La, Nd, Gd, Ho. Refined structures of compounds with Ln=La, Nd, Gd, Ho (sp.gr. P2sUb(1/n), z=2) point to their affinity with the cryolite structure. It is shown that mutual filling-up of a part of octahedral vacancies and octa-Vertex polyhedron with Ca and lanthanide atoms is observed in the structure. With an increasing difference in values of ionic radii a predominant filling-up of octa-vertex polyhedrons with Ca atoms occurs while octahedral vacancies with 0,0,1/2 coordinates are filled up with lanthanide atoms