Solid-state NMR techniques were applied for structural analyses of the plasma polymerized acrylonitriles. Secondary (–CH2–C≡) and tertiary carbons (=CH–C≡) were formed in the plasma polymerization of acrylonitriles. In addition to the formation of carbon double bonds (–CH=CH–), amide bonds (–CONH–) were also formed. The film formed at 100 W had a higher cross-linking structure than that formed at 20 W. The film produced from acrylonitrile with nitrogen gas contained carbons adjacent to nitrogen atoms (≡CH–N=). Near the electrode, nonprotonated carbons adjacent to nitrogen atoms (≡C–N=) were formed in the plasma polymers. These structural analyses contributed to elucidation of the plasma polymerization mechanism.