Summary The reaction of a hydrated nitrate salt of lanthanide (Ln=Pr, Nd, Gd, Dy, Er) with the polyfunctional ligand salicylhydroxamic acid (H3sha), in the presence of base, afforded solid compounds, insoluble in common organic solvents and in water. The new complexes characterized by means of elemental analyses (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are neutral, with a possible polymeric structure of the general type: [Ln2(Hsha)2(H2sha)(DMF)x(CH3O)(H2O)]n×2H2O Their thermal decomposition was studied in nitrogen and/or oxygen atmosphere, between 25-1000°C by using simultaneous TG/DTG-DTA technique. The IR spectroscopy used to determine the intermediates and the final products. The intermediates at 180°C suggest the formation of N-hydroxylactam complex, which upon further heating gives a carbonaceous residue of Ln2O3 at 1000°C in nitrogen, while in oxygen the stable oxides are formed at 600°C.