The UV-visible spectroscopic study of the interaction between rac-Et(Ind)(2)ZrCl2 and different aluminoxanes, such as isobutylaluminoxane (BAO) and ethyl(isobutyl)aluminoxane (EBAO), was conducted under normal polymerization conditions. UV-visible absorption spectra of rac-Et(Ind)(2)ZrCl2/aluminoxanes were correlated with the formation of ionic zirconium species. The influence of different aluminoxanes on the tightness of the metallocenium-aluminoxane ionic pairs was interpreted in terms of the aluminoxane structure. The loose ionic pairs formed in the EBAO system causes a fast decaying kinetic profile, advantageous for copolymerization.