Simulations of the spectra of vibrational transitions in highly vibrationally excited XY6 molecules at certain energy E-vib are performed. The infrared (IR) transitions in the mode upsilon(3) of the molecules SF6 and WF6 as well as the Raman ones in the mode upsilon(1) of SF6 ate studied. The shapes and parameters of the spectral bands, such as the integral intensity, the mean frequency, and the width, are obtained in a wide range of E-vib The calculated widths prove to be much broader than the expected contributions to them because of intramolecular vibrational relaxation (IVR); this indicates the dominant role of statistical inhomogeneous broadening in the width formation for the investigated molecules.