Abstract <p>Nuclear fragmentation reactions are important to study the characteristics of nuclear matter, to produce secondary beams and to obtain new isotopes. It is necessary to be able to predict the yields of isotopes produced in these reactions. Different models exist which allow to make the predictions of these quantities. In this report transport-statistical approach is discussed. The comparison of model calculations with experimental data obtained with the COMBAS set-up at Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nucler Research for the collisions of ¹⁸O (35 MeV per nucleon) beam with ⁹Be and ¹⁸¹Ta targets and with several well known models is presented. The target dependence of isotope ratios is studied. Its behaviour is explained by the strong correlation between the mass of a secondary fragment and an impact parameter of the reaction. The different pathways of reaction dynamics in case of heavy and light targets are discussed.</p>