Abstract: To investigate the influences of filter type and filter length on filtration efficiency of benzene and its homologues (toluene, ethylbenzene, p-xylene, m-xylene, o-xylene and styrene) in mainstream cigarette smoke, nine Virginia type and two blended type cigarettes with different filters and/or different lengths were tested under ISO and Health Canada intense (HCI) smoking regimes. The levels of benzene and its homologues were determined and the filtration efficiencies of these filters were compared. The results showed that: 1) The levels of benzene and its homologues in mainstream cigarette smoke under HCI smoking regime were significant higher than those under ISO. 2) Smoking regime, filter type and filter length affected the filtration efficiency to these smoke analytes. However, their effects on the filtration were slightly different depending on the exact smoke analyte. The filtration efficiencies were in the order of active carbon combined filter> polypropylene fiber filter> cellulose acetate filter> paper-acetate combined filter. The filtration efficiency to benzene and its homologues increased with the increase of filter length. The filtration efficiency under ISO smoking regime was about double that under HCI smoking regime. The benzene and its homologues were filtered by the filters in the order of styrene＞ o-xylene＞ (≈)p-xylene＞ m-xylene＞ ethylbenzene＞ toluene＞ benzene.