Abstract: In order to investigate the effects of expanded cut stem, expanded cut tobacco or reconstituted tobacco inclusion on the deliveries of harmful components in mainstream cigarette smoke, 15 cigarette samples containing different proportions of expanded cut stem, expanded cut tobacco or reconstituted tobacco were prepared. All cigarette samples were of the same hardness. Nine harmful components (tar, nicotine, CO, HCN, NNK, NH₃, BaP, phenol and crotonaldehyde) in mainstream smoke of the samples were determined, and the mathematical regression equations describing the relationship between these analytes and the proportion of the said inclusions were established. The results showed that: 1) the proportion of expanded cut stem, expanded cut tobacco or reconstituted tobacco increased by 10%, the cut filler weight of cigarette decreased by 1.8%, 3.1% or 1.3%, respectively, puff number decreased by about 0.4 puffs. When the proportion of expanded cut tobacco or expanded cut stem increased by 10%, the draw resistance of cigarette increased by about 3.0%; 2) with the increase of the proportion of expanded cut stem, the deliveries of CO and crotonaldehyde increased while that of the other harmful components decreased; with the increase of expanded cut tobacco proportion, the delivery of crotonaldehyde increased while tar, nicotine, CO, BaP, NH3 and phenol deliveries decreased. With the increase of reconstituted tobacco proportion, the delivery of crotonaldehyde increased while tar, nicotine, HCN, BaP, NH3 and phenol deliveries decreased; 3) NH3, BaP and phenol deliveries could be selectively decreased by increasing the proportion of expanded cut stem, expanded cut tobacco or reconstituted tobacco.