According to picosecond radiolysis data, primary radical cations in irradiated carbonates are very rapidly deprotonated. At the same time, analysis of the radiation-induced fluorescence from carbonate solutions indicates the formation of solvent-related radical cationic species with a relatively long lifetime. We use quantum chemical methods to develop a model of carbonate ionization that reconciles these conflicting data. Using ethylene carbonate as an example and assuming that its molecules exist in solution as a collection of dimeric associates, we show that both processes are the result of the loss of an electron from such dimers. This demonstrates that the generally accepted conceptualization of a primary ionization event, based on the idea of the formation of a radical cation of an individual molecule of an irradiated substance, requires revision in the case of polar aprotic liquids that tend to form molecular associates.