FTIR spectra of the vHF bands in B/HF mixtures (B¼Xe, CO2, CO, HCN, CH3CN) have been recorded with densities varying from the dilute gas to liquid at room temperature. The vibration–rotational bands of free HF molecules in all systems were calculated for the density ranging from 1 to 400 amagat, and, by separating the bands, the vHF band shape of bound molecules were determined. It was shown that on transition from the gas to liquid phase the mHF band of B...HF complexes shifts toward low frequencies and symmetrizes. The vibration-rotational vHF band of these complexes in the gas phase was calculated using a model with the anharmonic coupling between mHF and low-frequency vibrational modes. It was established that the model taking into account the spectral exchange applied to a system consisting of rotational and low-frequency vibrational subsystems provides a correct description of evolution of the mHF complex band with increasing density.