Doppler broadening spectroscopy (DBS) using a slow positron beam has been applied to investigate degradation induced by 200 keV electrons irradiation in polyetherurethane (PU). The low momentum fraction S (and respectively the high momentum fraction W) characteristic of the irradiated films is shown to decrease (and respectively to increase) when the electron deposited energy increases. The DBS results are compared to the mass loss measured by 'solvent swelling' of the films which shows that the cross-linking increases as the electron deposited energy increases. (C) 2002 Elsevier Science B.V. All rights reserved.