Abstract A thermospray discharge ionization source has been used to obtain a collisionally induced dissociation (CID) spectrum of nabilone (MW 372) using a single stage quadrupole mass spectrometer. The resulting CID-mass spectrometry (MS) data show only a few structural features. Since most of the important fragments are above mass 200, it is difficult to assign structural identities to the primary daughter fragments or the nabilone molecule. Further information was obtained by using the thermospray discharge ionization source with a triple stage quadrupole mass spectrometer. Selected primary daughter ions were subjected to a second stage of CID fragmentation. Many of the resulting granddaughter ions are now in the mass range of 50–150 daltons and confident structure assignments can be made. The CID-MS—CID-MS data on nabilone showed the following features: a C 9 aliphatic chain with a branch giving a C 6 chain; losses of masses 58, 86, and 100 suggesting a ketonic structure that can break with up to 6 aliphatic carbons; losses of masses 60, 61, and 102 suggesting an ether or alcoholic oxygen; presence of one aromatic ring with one or two phenolic oxygens; low mass fragments of masses 55, 69, and 83 indicative of rings or unsaturation. It is audacious to suggest that the information given here is sufficient to write the full structure of nabilone. Nevertheless, the granddaughter fragment information permits a reasonable reconstruction of possible structures that could not be made with the first-order collisional fragmentation.