The electrochemical carboxylation of some arylmethyl chlorides RCl [R = benzyl, 4-methoxybenzyl, 4-(trifluoromethyl)benzyl or diphenylmethyl] catalysed by [Co(salen)][H₂salen =N,N′-bis(salicylidene)-ethane-1,2-diamine] was studied in acetonitrile. Comparable amounts of carboxylic acids and saturated hydrocarbons were obtained when R = PhCH₂ or 4-MeOC₆H₄CH₂ whereas carboxylic acids were the main products with R = 4-F₃CC₆H₄CH₂ or Ph₂CH. Electrogenerated [Co^I(salen)]^– reacts with RCl to give an organometallic complex, [Co^III(salen)R], with a rate constant which, for all chlorides investigated, is of the order of 10⁵ dm³ mol^–1 s^–1. The one-electron-reduced complex [Co^II(salen)R]^– is unstable and its decomposition in the presence of CO₂ is the key step of the electrocatalytic process. Different decomposition pathways are considered and their mechanistic implications discussed. In the presence of proton donors [Co^II(salen)R]^– undergoes rapid hydrolysis to RH and [Co(salen)].