The cross-linked polymer EnCat (TM) 40 (polyurea) is investigated on the micro-(ESEM) and nanometer scale (ISEC, ESR, C-13 CP MAS NMR) both in the dry (ESEM, C-13 CP MAS NMR) and in the swollen state.(ISEC, ESR, C-13 CP MAS NMR). After swelling with THF or DMF, nanoporous domains featured by ca. 1.2 nm pores are clearly detected with ISEC. ESR analysis based on the evaluation of the rotational mobility of a suitable spin probe dissolved in THF, DMF, MeOH and PhCH3 as swelling media, does qualitatively confirm the presence of nanoporosity also in MeOH- and PhCH3-swollen EnCat (TM) 40. Our manifold analysis reveals the lack of any detectable nanoporosity in water. (c) 2007 Elsevier B.V. All rights reserved.