Solid particle erosion of epoxy resin (EP) modified by various amounts of hygrothermally decomposed polyester-urethane (HD-PUR) was studied at oblique (30, 45, and 60 o ) and normal impact (90 o ). The cross-linked structure of the modified EP was characterised by the mean molecular weight between cross-links (M c ). It was established that the initial brittle erosion of the densely cross-linked EPs (M c =<200g/mol) changed to a rubbery one by increasing HD-PUR modification due to which a less cross-linked network was formed (M c >1000g/mol). This change was reflected by the impact angle dependence: compositions of low M c showed the minimum resistance at normal (90 o ), whereas those of high M c at 30 o impact angle. The resistance to solid particle erosion changed linearly with increasing fracture energy (G c ) of the resins. G c , on the other hand, followed the prediction of the rubber elasticity theory and increased linearly with M c 1 / 2 .