Abstract: In order to investigate the influences of filter ventilation on the releases of acidic components in mainstream cigarette smoke, the levels of acidic components in mainstream smoke of cigarettes with different filter ventilations were determined by GC/MS. The results showed that:1) The releases of main acids, including formic acid, acetic acid, lactic acid, palmitic acid, linoleic acid, linolenic acid, oleic acid and stearic acid, accounted for more than 90% of the total release of the tested 25 acidic components in mainstream cigarette smoke. These acids had an important contribution to overall smoke pH. The releases of the other acidic components were low, they played an important role in harmonizing smoke sensory quality. 2) With the increase of filter ventilation rate, the releases of the 25 acidic components and the total release of all the acidic components in mainstream smoke decreased gradually, however their degree of decrease differed greatly. 3) With the increase of filter ventilation rate, the contributions of the 25 acidic components to the total release of acidic components in mainstream cigarette smoke differed remarkably, some made positive contributions, some made negative contributions, and the others kept unchanged basically.