Abstract The aim of this study is to evaluate the removal efficiency of iopromide using electron beam (E-beam) irradiation technology, and its degradation characteristics with hydroxyl radical (OH) and hydrated electron (eaq−). Studies are conducted with different initial concentrations of iopromide in pure water and in the presence of hydrogen peroxide, bicarbonate ion, or sulfite ion. E-beam absorbed dose of 19.6kGy was required to achieve 90% degradation of 100μM iopromide and the E-beam/H2O2 system increased the removal efficiency by an amount of OH generation. In the presence of OH scavengers (10mM sulfite ion), the required dose for 90% removal of 100μM iopromide was only 0.9kGy. This greatly enhanced removal was achieved in the presence of OH scavengers, which was rather unexpected and unlike the results obtained from most advanced oxidation process (AOP) experiments. The reasons for this enhancement can be explained by a kinetic study using the bimolecular rate constants of each reaction species. To explore the reaction scheme of iopromide with OH or eaq− and the percent of mineralization for the two reaction paths, the total organic carbon (TOC), released iodide, and intermediates were analyzed.