[en] Synthesis and structure-chemical investigation of benzoates for all REE is carried out, their composition is determined, they are shown to be divided into two groups according to the hydrate composition: Ln(C₆H₅COO)₃x3A₂O (where Ln=La, Ce → Gd) and Ln(C₆H₅COO)₃x5H₂O (where Ln=Tb→Lu, Y). Their IR spectroscopic and X-ray investigation is carried out; three isostructural groups: 1) La, Ce, Pr, Nd; 2) Sm, Eu, Gd; 3) Tb, Dy, Ho, Er, Yb, Lu and Y, are determined. Thermal decomposition is investigated, intermediate and final products of thermolysis are established. The crystal structure of the representative of the third isostructural group Dy(C₆H₅COO)₃x5H₂O is determined