In the framework of the title problem we have performed quantum-chemical calculations (DFT B3LYP method) of some ionic liquids (ILs) possessing the common anion tetrafluoroborate. The computational data have shown that for any ionic pair of all the considered ILs their HOMOs are localized mainly on their negative charged heteroatoms (F, O, N) while the atomic orbitals of their positive charged hydrogen atoms and the sp2-hybridized carbon atoms enter the LUMOs. It is clear that the attractive interaction forces between two neighboring ionic pairs will appear due to all the possible atom-atomic interactions between the heteroatoms and the positive charged hydrogen and carbon atoms. Since these attractive interactions lower the potential energy of two-particle interactions, it is logical to assume the existence of some kind of correlation between their number and the critical temperature Tc of the ILs. To find this correlation dependence we use for any ionic pair the following numbers: N_H – the number of its hydrogen atoms, N_C – the number of sp2hybridized carbon atoms, the number N = N_H +N_C, and N_HA – the number of the heteroatoms. The last value is the sum of the heteroatoms belonging to both the cation and the anion. It is obviously, the total number of all possible attractive interactions between the two ionic pairs, will be equal to the product P = 2N*N_HA. The following correlation analysis allows one to reveal the very simple dependence between Tc and P: Tc=gVp, where g is a constant which equals to 44.56 K for all the considered ILs. The calculated values of Tc as well as the experimental ones [1] are given in the Table. We suppose that the found quantitative dependence will be will also be valid for otherseries of ionic liquids.In the case of [C27guan][BF4] the value of NHA was calculated by taking into account the spatial shielding of the two of its nitrogen atoms by four bulk hexyl groups