Abstract: The infrared spectroscopic investigations for the =CH and NH vibrations and the effect of substitution at different positions in the phenyl rings of 2-amino-4,6-diphenyl-3,6-dihydropyrimidines have been described. The CH stretchings were observed between 3070-3060 cm -1. The observed frequencies differ for –NH bending and the =CH and –CH stretching vibrations, and the difference between the two frequencies is larger than the predicted differences between scaled frequencies. It has been observed that the substitution of phenyl rings with –OH, -OCH3, -NO2 and –Cl groups, further complicated the elucidation of the spectra. The electronic transitions in the UV spectra were observed to be hypsochromic (blue shift) when a powerful electron donor group is present in the heterocyclic nucleus. Other electronic transitions were observed in the ultraviolet spectra to check the presence of - * and n- transitions in these compounds.