Electrooxidation of dipyridamole (DIP) and several of its derivatives, RA14, RA47, RA143 and RA25, was studied in acetonitrile. It is observed that all the derivatives (except RA143) like DIP, exhibit a consecutive two-step one-electron electrochemical oxidation. The oxidation potentials for DIP, RA14 and RA47 are quite similar, while those for RA25 are higher. The derivative RA143 which lacks two of the nitrogens linked in positions 2 and 6 of the pyrimido-pyrimidine ring is not electroactive in the potential window used. The spectral changes following oxidation were monitored by UV-vis optical absorption and ESR, which in conjunction were able to shed additional light on the species involved in the complex equilibrium. In the first wave process cation radicals of DIP and RA25 are produced which decay to the final products with half-lives of 160 and 90 min. The decay for the cation radical of RA25 is faster than that of DIP, due to its lower stability in ACN solution. The ESR spectrum of RA25 cation radical is very similar to that of DIP in agreement with recent theoretical calculations that show that the electron is removed from the conjugated system based on the pyrimido-pyrimidine ring. The analysis of the spectra registered after the two electron oxidation of DIP and RA25 derivative shows that while, for DIP the reaction produces one additional intermediate, for RA25 it leads directly to the final product(s).