A system for exhaust gas purification disposed in the exhaust pipe of an internal combustion engine, which includes a zeolite as adsorbent component capable of adsorbing the hydrocarbons present in the exhaust gas emitted from the engine and a catalyst capable of reducing the harmful substances present in the exhaust gas; the system satisfies the following conditions: a/c=3 to 50 cc/g, wherein a is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using N2, and c is the total amount of the hydrocarbons emitted from the engine during the period of 140 seconds from the start of the engine when the engine is operated in accordance with the LA-4 mode of FTP, thereby the adsorption capacity of the zeolite used as a HC adsorbent is optimized against the amount of the HC discharged from an engine during a certain period of the cold start so as to adsorb and purify the HC effectively.