Abstract: The crystal structures of PrCl₃·C₁₀H₂₀O₅ and SmCl₃·C₁₀H₂₀O₅ have been determined by X-ray diffraction analysis. The complexes are isomorph, and monoclinic with space group P2_1/c and lattice parameters: a=8.167 (2) [8.129(7)], b=14.225(3) [14.176(7)],c=14.208(4) [14. 117(5)]Å, β=104.78(2)[104.62(5)]°and Z=4.The rare earth ion is bonded to the three chlorine atoms on one side and to five oxygen atoms of the crown ether on the opposite side forming an irregular 8-coordinate polyhedron. Mean bond lengths of Ln-O 2.606[2.566]Å,of Ln-Cl, 2.714[2.666]Å, they are shorter than those in higher coordinate complexes.