A few hydrogen-bonded systems can be considered as polymers; hence, dispersion curves ν(k) and frequency distribution g(ν) can be calculated. In the present paper molecular vibrations of a single chain of hydrogen-bonded HF and DF are studied throughout the first Brillouin zone. k=0 fundamental modes are calculated. From ν(k) and g(ν) it is possible to propose a better interpretation of the previously reported inelastic neutron scattering spectrum. The limitations of the model used are discussed and suggestions for a more refined approach of the problem are given.