In many circumstances of data fitting one has to choose the optimal fitting function or model among several alternatives. Criteria or tests on which this decision is based are necessary and have to be well selected. In this preliminary analysis the application of the corrected Akaike information criterion is demonstrated considering the example of determining pharmacokinetic parameters for the blood serum time activity curves of 111In-labeled anti-CD66 antibody. Another model selection criterion, the F-test, is used for comparison. For the investigated data the corrected Akaike information criterion has proved to be an effective and efficient approach, applicable to nested and non-nested models.