Two types of nanostructures, nanowires and nanoribbons were prepared with polypyrrole (PPy) by controlling the concentration of acrylic acid (AA) in systems containing cationic surfactant, cetyltrimethylammonium bromide (CTAB) at about 12 degrees C. The effect of reaction conditions involving the concentration of AA, CTAB, pyrrole as well as the reaction temperature was systematically studied on the final structures of prepared PPy. The results revealed that the polymerization of AA, resulting in PAA, played a key role in the evolution of PPy nanostructures. A possible mechanism was briefly discussed on the formation of these two nanostructures, nanowires and nanoribbons.