Force fields have been calculated for 2-Chloro and 2-Bromo derivatives of Selenopnene and Tellurophene. The calculation of the fundamental frequencies was performed starting from a GVTF which was proven satisfactory for the heter-ocyclic parent molecules. In the initial steps we refined only the force constants mostly involving the substituent vibrational modes. In the final step, some force constants involving the ring motions were also released, in order to obtain the best fit. The procedure has been developed with the aim of getting information on the influence of the substituent effects on the heteroaromatic ring force field.