Abstract Nine monosaccharides and four disaccharides were mass analyzed using a quadrupole time‐of‐flight tandem mass spectrometer combined with an electrospray ionization source. Product ion mass spectra of deprotonated, protonated, and sodiated saccharides were observed and were compared within each group of saccharides. Each of the deprotonated pentoses, hexoses and disaccharides yielded a significantly different product ion mass spectrum with the exception of α ‐lactose and β ‐lactose. The disaccharides α ‐ and β ‐lactose differ only at the glycosidic linkage. Product ion mass spectra of protonated and sodiated α ‐ and β ‐lactose were indistinguishable also. Copyright © 2005 John Wiley & Sons, Ltd.