Reactions between lanthanide cations (form La+ to Lu+ except Pm+) and methanol clusters were studied in a pick-up source, and the product ions were analyzed using a reflectron time-of-flight mass spectrometer (RTOFMS). Those reactive ions including La+, Ce+, Pr+, Nd+, Gd+, Tb+, Ho+, Er+, and Lu+ react with methanol molecules forming dehydrogenation products LnCH(2)O(+) and EnCH(3)O(+). For large clusters, the dehydrogenation products become Ln(OCH3)(2)(CH3OH)(n-2)(+). On the contrary, the relatively unreactive lanthanide ions including Sm+, Eu+, Dy+, Tm+, and Yb+ do not react with the methanol molecules. Only when they are solvated by a sufficient number of methanol molecules does dehydrogenation occur and yield Ln(OCH3)(2)(+)(CH3OH)(n-2)(LnOCH(3)(+)(CH3OH)(n-1) for Eu+). The relative reactivities of these ions are discussed in terms of their electronic configurations. Reactions of LnO(+) with methanol clusters lead to water elimination and produce LnO(2)C(2)H(6)(CH3OH)(n-2)(+). As cluster size increases to n approximate to 13, the reaction is quenched, and only the association products LnO(CH3OH)(n)(+) are formed.