Halfwidths and shifts of HF-HF R0 line centers belonging to high vibrational bands lying near the dissociation threshold have been estimated in the case of self-broadening for the first time. A considerable narrowing (up to 25 percent) was found for the lines of 0-22 HF band compared to the rotational band. The decrease in halfwidths is explained by the fact that the mean dipole moment and the absorption constant of the molecule strongly change as the molecule is vibrationally excited. It has been found that the line shifts increase due to increase of the absorbing molecule polarizability upon its vibrational excitation.