Mechanism of hydride transfer reactions to form olefins is still a conundrum. Here, we propose an electron transfer (ET) followed by hydrogen atom transfer (HT) as the most likely mechanism for hydride transfer reactions from the hydride adducts of olefins (G-XH-) to a carbocation (T+) in acetonitrile. This is confirmed by the analysis of the energetics of each mechanistic step, estimated from Delta H-H(-) (the hydride affinity) and redox potentials of the related species, and activation energetics calculated from rate constants of the hydride transfer from G-XH- to T+.