AbstractThe behaviour of all nine chlorinated veratroles (1,2‐dimethoxybenzenes) under electron impact has been investigated. The most common fragmentation processes are interpreted using metastable ion analysis and deuterium labelled compounds. For all compounds studied, the most common fragmentation route seems to be the primary loss of a methyl radical followed by loss of carbon monoxide. The ion formed has a well‐known quinonoid structure and fragments by several routes elucidated by metastable ion analysis. In general, the spectra of the positional isomers are shown to be practically similar and it is apparent that e.g. the 3‐ and 4‐chloro isomers can be differentiated only from the abundance ratio of the [MCH3COCH3]+and [MC