Novel hetero-tri-spin coordination polymers formed of ring-shaped Cu-nitronyl nitroxide spin clusters and LnIII linkers are reported. These mixed 2p-3d-4f compounds of formula {[Ln(hfac)3][Cu(hfac)2(NIT-3Py)]2·C6H14}n [LnIII = Y (1), Gd (2), Tb (3), and Dy (4); NIT-3Py = 2-(3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexa-fluoroacetylacetonate], exhibit a 1D chain structure consisting of [Cu(NIT-3Py)]2 rings linked by Ln(hfac)3 units. Their magnetic behavior is characteristic for ferromagnetic interactions between the metal centers and the coordinated radical units. The Tb derivative was found to exhibit slow relaxation of its magnetization.