The mass spectral fragmentation of 2-adamantanone has been investigated using its specifically labelled monodeuterated derivatives (in positions 1-, 4-exo-, 4-endo-, 5- and 6-) and dideuterated derivatives (in positions 4,4- and 6,6-). The mass spectrum of 2-adamantanone is generally poor in fragments showing the molecular ion as the base peak, the characteristic m/z 117, 104, 93, 91, 80, 79, 72, 67 and 53 fragments, as well as an unusual loss of water. The mass spectra of deuterated compounds favours the assumption of hydrogen randomization prior to the fragmentation of the molecular ion. In contrast, the formation of [C4H8O], m/z 72 does not involve any major hydrogen scrambling.