This work describes relevant structural features of the ternary Li-Mn-MgO system useful for the reaction of methane oxidative coupling. For a Mn-MgO catalyst, XRD, XPS, and ESR techniques revealed that manganese is incorporated into a Mg6MnO8 phase in which the formal oxidation state of manganese is Mn4+, Addition of Li2CO3 in small amounts (0.48-1.60 wt. % Li) to the base Mn-MgO catalyst results in partial destruction of the Mg6MnO8 phase. TPR and XPS data showed that the reduction of manganese is easier in the bulk Mg6MnO8 compound than in the Mn-MgO catalyst and that it is inhibited by lithium. Moreover, the increase in Mn/Mg XPS intensity ratios in the lithium-doped counterparts indicates that lithium incorporation into the base Mn-MgO catalyst enhances manganese dispersion, in agreement with the increase of Mn4+-Mn4+ distance derived from ESR spectra.