In this paper, virgin polyethylene tere phthalates has been blended in an elastic extruder with three different types of polyrpoylenes such as low viscoity polypropylene (A 50 12), high visocity PP ( K 7050) and modifed (XXP 707W). Dynamic mechanical behaviour such as storage modulus (Er) and dissipation factor (tax) of these blends has been determined at different temperatures. Effects of blending ratio on storage modulus and dissipation factor have been determined, compared and analyzed. It has been found that addition of PET increased the storage modulus of PP due to the higher modulus of PET. An additional peak has been observed in tan plots obtained for PP/PET blends. This additional peak corresponds to a- relaxation of PET. Type of PP addition has also modified the dissipation factor (Tan d) and storage modulus Er behavious of blends