TMEDA and its ethyl-substituted analogue, TEEDA, show a different behavior toward the deprotonation with lithiumalkyls. While TMEDA mainly undergoes alpha-lithiation of its methyl group, TEEDA shows selective beta-lithiation with following elimination of ethene. The crystal structure of the monomeric intermediate of this beta-lithiation, tBuLi.TEEDA, and theoretical studies indicate kinetic favoritism for the beta-lithiation.