Abstract Investigations concerning the nature of interactions must be considered an issue of primary importance in the chemical sciences. The dynamic and static natures of interactions were recently proposed based on the quantum theory of atoms in molecules dual functional analysis (QTAIM‐DFA). The nature of interactions is widely investigated under various conditions, which often results in the predictions of (very) different natures. The predicted nature should be well correlated to the observed parameters, especially for experimental scientists. The effects from the basis sets and levels of calculations on the predicted parameters are carefully examined, exemplified by the interaction distances in question, the QTAIM functions for the interactions, and the QTAIM‐DFA parameters. The effects are discussed for the total (basis set + level) terms and each term. The mechanisms of the total terms are also clarified for the QTAIM‐DFA parameters. The results provide a good guideline for discussion of the nature of interactions based on the calculated parameters under various calculation conditions. The results help to establish a reliable method to elucidate the nature of interactions, such as QTAIM‐DFA.