A 25 mu m thick polystyrene (PS) film was implanted with 120 keV ions of carbon to doses of 1 x 10(14), 1 x 10(15), 3 x 10(15), 5 x 10(15) and 1 x 10(16) ions cm(-2), respectively. The structure of the implanted PS was characterized by X-ray photoelectron spectroscopy (XPS), whereas the friction and wear behaviour of both implanted and unimplanted PS were investigated using an one-way reciprocating friction tester against a steel ball. Friction results indicate that ion implantation at a dose of 1 X 10(14) ions cm(-2) increases friction coefficient, whereas the ion implantation at a dose of 1x10(15) ions cm(-2) or higher decreases friction coefficient, and all the tests show that ion implantation lowers wear rate. XPS analyses reveal that ion implantation at dose of 1x10(14) ions cm-2 results in partial break of benzene ring, and at a dose of 1 x 10(16) ions cm(-2) results in complete break of benzene ring.