AbstractConventional partition function of free internal rotation shows incorrect limit behaviour for low temperatures and small values of reduced moment of inertia. Consequences of transition to the new formula with correct limit behaviour regarding calculations of thermodynamic functions have been studied for CH3NO2, C6H5NH+, C6H5, – C6H5, CIF, HF · HF CIF, CF3H · OH2, CCl3H · OH2· C3H6OH2, (H2)2, and (H2O)2. In the case of association of HF and CIF the thermodynamic characteristics of the overall process have also been recalculated in the terms of the newly suggested approach. It has been shown that application of the new formula can cause substantial changes inH T0andS T0values in the region of not only low but also moderate temperatures. Corrections of values of the thermodynamic characteristics which are required by this improved procedure can be more significant than or comparable with the values of corrections with respect to deviations from behaviour of rigid rotator or harmonic oscillator. As a side product the study points out a number of numerical errors and non‐reproducibilities of the earlier reported values based on the conventio