Abstract: The complexation of 2,3-dihydroxy-p-xylenediiminotetraacetic acid (DPTA) with Ca²⁺,Th⁴⁺ and diamagnetic rare earth ions La³⁺, Lu³⁺, Y³⁺ and Sc³⁺ has been investigated by ¹H NMR and UV VIS absorption spectroscopy methods in this work. Based on the NMR results it is concluded that the reaction of DPTA with the diamagnetic RE ions is a slow exchange reaction, while that with Ca²⁺ is a fast one. The compositions of the complexes are as follows: Th⁴⁺ with DPTA forms 1:2 complex and the other ions Ca²⁺, La³⁺, Lu³⁺, Y³⁺ and Sc³⁺ mainly form 1:1 complexes. The compositions of the complexes are dependent on the pH of the solution. The chemical shift variatfons (△δ) on NMR spectra of dismagnetic RE complexes with DPTA have been compared with λ_max variations (△λ) of UV absorption spectra. A similar order in change was found for both △δ and △λ: Sc³⁺3+≈Lu³⁺ <3+.