Polytetrafluorethylene (PTFE and ePTFE) substrates were treated by ion implantation with nitrogen ions of 20 keV energies and 10(13)-10(16) ions/cm(2) ion fluences. The modification of the polymer surface was analyzed by FTIR and XPS spectroscopy, water wetting angle measurements and AFM images. The surface morphology, wettability and chemical activity were changed due to surface modification. The growing of endothelial cells of modified surfaces was improved in comparison with untreated PTFE and ePTFE substrates. The improved cell adherence on the modified surface is based on the improved adhesion of cell proteins. (C) 2014 Elsevier B.V. All rights reserved.