The stoichiometric reduction of N-carbophenoxypyridinium tetraphenylborate (6) by CpRu(P-P)H (Cp = η 5 -cyclopentadienyl; P-P = dppe, 1,2-bis(diphenylphosphino)ethane or dppf, 1,1′-bis (diphenylphosphino)ferrocene) and Cp*Ru(P-P)H (Cp* = η 5 -pentamethylcyclopentadienyl; P-P = dppe) gives mixtures of 1,2-and 1,4-dihydropyridines. The stoichiometric reduction of 6 by Cp*Ru (dppf)H (5) gives only the 1,4-dihydropyridine, and 5 catalyzes the exclusive formation of the 1,4-dihydropyridine from 6, H 2 , and 2,2,6,6-tetramethylpiperidine. In the stoichiometric reductions, the ratio of 1,4 to 1,2 product increases as the Ru hydrides become better one-electron reductants, suggesting that the 1,4 product arises from a two-step (e − /H•) hydride transfer. Calculations at the UB3LYP/6-311++G(3df,3pd)//UB3LYP/6-31G* level support this hypothesis, indicating that the spin density in the N-carbophenoxypyridinium radical (13) resides primarily at C4, while the positive charge in 6 resides primarily at C2 and C6. The isomeric dihydropyridines thus result from the operation of different mechanisms: the 1,2 product from a single-step H − transfer and the 1,4 product from a two-step (e − /H•) transfer.