Vinyl carbanions derived from cis-cinnamonitrile 1 were formed by reacting it with lithium diisopropylamide (LDA) as a base in aprotic solvents at low temperatures; reaction with various electrophiles (E) resulted in the corresponding derivatives PhCHC(E)CN. The configurational stability of the vinyl carbanions derived from 1 and the geometry of the reaction products was affected by the solvating properties of the medium. Retention of configuration was achieved in a poor solvating medium-diethyl ether-hexane (4:1). Addition of a crown ether or using THF as solvent resulted in products having trans geometry. The site of deprotonation of cinnamonitrile (cis and trans) was compared to that of cinnamic esters and discussed. Determination of the geometry of the products was based on their 1H NMR spectra.