The gas phase reactivity of small cationic cobalt clusters, Co n + (n=1-12), towards methanol has been investigated using Fourier transform ion cyclotron resonance mass spectrometry. Sequential addition of methanol molecules to the clusters was observed to be the dominating process, with the exception of Co 4 + and Co 5 + , for which dehydrogenation of methanol was the dominating initial reaction step. Isotopic labelling studies with CD 3 OH showed that the dehydrogenation is a 1,1-elimination reaction involving the methyl group. Loss of a cobalt atom upon methanol addition was also observed to be a facile process, being most pronounced for Co 2 + , Co 3 + and Co 6 + .