Abstract: Neutral cobalt carboxylates are converted into their basic forms in the ion source during vaporization. The three most abundant peaks in EI spectrum of every salt are Co_4O(OCOR)_5~(+·) , Co_4O(OCOR)_5+ and Co_2O(OCOR)_3~+. The protonated molecular ion in i-C_4H_(10)-CIMS is the base peak. NI spectra of cobalt carboxylates are unique in that they are dominated by the base peak of the molecular ion Co_4O(OCOR)_6~- and ± 14n amu peaks on either side of it. The explanation for the formation of ions through gaining and losing multiples of CH_2 units is not yet clear and further investigation is required.