Some thorium(IV) complexes were synthesized with the tetradentate Schiff base ligands (N2O2 donor set) obtained by the condensation of ethylenediamine with salicylaldehyde (H2salen) or acetylacetone (H2 acacen). In all cases the neutral Schiff bases and not their anions are coordinated to the central thorium(IV) atom. The complexes have the general formula: ThL2Xa (L = H2 salen; X = Cl, Br, 1, NCS and L = lie acacen; X = Cl, 1, NCS, ClO4) or ThLX4 (L = H2 salen; X = NO3, ClO4 and L = H2 acacen; X = Br, NO3). The stoichiometry and coordination number of the complexes was determined on the basis of elemental analysis, conductivity measurements, i.r. spectra and t.g.a./d.t.a. data. The coordination number of the complexes is either 12 or 8 for the bisor monocomplexes respectively.