Abstract From the aerial parts of Chromolaena tyleri, five 4′-hydroxyflavanones have been isolated. By methylation their 4′-methoxy derivatives were obtained. Comparing their El-mass spectra, a significant fragment with 4′-hydroxyflavanones was detected, but not with 4′-methoxyflavanones. We therefore propose a characteristic fragmentation of 4′-hydroxyflavanones.