<jats:p>The mass spectra of some naturally occurring and synthetic α- and γ-pyrones, benzofurans, and 2,2-dimethylchromenes have been determined. Under electron impact compounds derived from coumarin lose oxygen atoms as CO, usually forming a stable benzofuran ion. 2,2-Dimethylchromenes lose a methyl radical to give a stable benzopyrylium ion, while the most prominent fission of flavanoid compounds occurs by breaking both bonds β to the A ring.