The infrared bands of cis- and trans-CHCH and vinyl CHCH 2 groups of 1-hexene, trans-2-hexene, trans-3-hexene, 1-heptene, trans- and cis-2-heptene and cis-3-heptene are compared spectroscopically with the bands of the analogous chemical groups in six stereospecific and non-stereospecific polybutadienes with different cis-, trans- and vinyl microstructural composition. Special attention is given to the bands associated with the vibrations of the in-plane and out-of-plane CH deformation modes. The bands of the cis- and trans-CHCH groups appear at 1411-1405, 1310-1300, 1313-1310 and ≈ 1298 cm −1 for the cis ρ(CH)a, cis ρ(CH)s, trans ρ(CH)s and trans ρ(CH)a modes respectively of the olefins and polybutadienes. The trans ω(CH) mode appears at 975 cm −1 (with a band-width at half height of 16 cm −1 ) or 967 cm −1 (with a band-width of 21 cm −1 ) in the spectra of the olefins and the polybutadienes respectively. These values contrast sharply with those of the cis ω(CH) mode. The spectra of the olefins show that this mode absorbs infrared radiation at 713 cm −1 and has a band width at half height of 32 cm −1 for cis-2-heptene, or at 698 cm −1 with 44 cm −1 band-width for cis-3-heptene. The spectra of the polybutadienes show that the maximum absorption of this mode appears between 728 and 739 cm −1 with band-widths that vary between 70 and 40 cm −1 . These observations indicate that the exact position and band-width of the cis ω(CH) is therefore very dependent on the configuration of the adjacent units, and possibly of units further removed. The bands of the vinyl group appear at 1422-1419, 1308-1295, 995 and 913 cm −1 for the δ(CH 2 ), ρ(CH), trans ω(CH)ip and ω(CH 2 ) modes of the olefins and polybutadienes. The cis ω(CH)ip mode splits into two bands at 632 cm −1 and 554 cm −1 in the spectra of the olefins; these bands are associated with the cis and skew rotational isomers of the olefins. Unfortunately these bands are not observed in the spectra of the polybutadienes because of the strong and broad absorption of the cis ω(CH) mode.