In order to improve the cytocompatibility of polyurethane (PU) porous scaffolds obtained by thermally-induced phase separation, poly(hydroxylethyl acrylate) (PHEA) was covalently immobilized by grafting copolymerization of HEA by photo-oxidation of the scaffolds and initiation of UV light. FT-IR-ATR spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations confirmed the occurrence of the grafting co-polymerization of HEA on the porous PU scaffolds. The measurement of water absorption demonstrated the improvement of the hydrophilicity after grafting with PHEA. The results obtained in a human umbilical vein endothelial cell (HUVEC) culture proved that the porous PU scaffold modified with the hydrophilic PHEA had better cytocompatibility than the control. The influence of surface pore size on the HUVEC growth behavior was assessed regarding cell anchorage, proliferation and viability, as well as morphology. An overall increase of cell number and viability with the decrease of the surface pore size was found.