Alkyl dinitrites have attracted attention as an important type of nitrosating agent and a pollution source in atmosphere. The reactivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are relatively unknown. In this work, decomposition of 1,3-cyclohexane dinitrite and 1,4-cyclohexane dinitrite are studied by electron impact ionization mass spectroscopy (EI-MS). Apart from NO<sup>+</sup> (m/z 30), fragment ions m/z 43 and 71 are most abundant for the 1,3-isomer. On the other hand, fragments m/z 29, 57, 85 and 97 stand out in the EI-MS spectrum of 1,4-isomer. Possible dissociation mechanisms of the two dinitrites are investigated by theoretical calculations. The results reveal that the ring-opening of 1,3-cyclohexane dinitrite mainly starts from the intermediate ion (M-NO)<sup>+</sup> by cleavage of two αC-βC bonds. For 1,4-cyclohexane dinitrite, in addition to the decomposition via intermediate (M-NO)<sup>+</sup>, cleavage of βC-βC bonds can occur directly from the parent cation M<sup>+</sup>. The results will help to understand the structural related chemistry of alkyl dinitrites in atmosphere and in NO transfer process.