A combination of a fluidized bed and a low pressure plasma has been employed for the surface modification of low density polyethylene (LDPE) powders. Optical Emission Spectroscopy and Laser Doppler Anemometry has been used for the characterization of the reactor. XPS and contact angle measurements were carried out to reveal surface modification of nitrogen and ammonia plasma treatment of LDPE powders. Both nitrogen and ammonia plasma treatment show an increase of the hydrophilic character of the surface treated LDPE powders. XPS analysis shows the incorporation of new functional moieties including C-N, C-O groups on the surface of treated powders. In this configuration nitrogen plasma treatment leads to a better incorporation of nitrogen containing functional groups when compared to ammonia plasma. (C) 2004 Elsevier B.V. All rights reserved.