A low power atmospheric pressure helium plasma torch was used to modify the surface chemistry of poly(α-methylstyrene), polystyrene, poly(propylene) and polyethylene. Mass spectra of the positive ions present in the plasma during the treatment revealed dominant -ions with structures that reflected the structure of the polymer, e.g. C6H5CnH 2n containing a phenyl group in the aromatic polymers and hydrocarbon structures CnH2n±1 up to n = 14 for poly(propylene). Ions up to m/z 300 were detected. X-ray photoelectron spectroscopy showed that this treatment introduced oxygen-containing functional groups into the surface of the polymers.