The present invention comprises 6,8-difluoro-7-hydroxycoumarins and derivatives of 6,8-difluoro-7-hydroxycoumarins, including reactive dyes, dye-conjugates and enzyme substrates. These fluorine-substituted fluorescent dyes typically possess greater photostability and lower pH sensitivity in the physiological pH range than their nonfluorinated analogs, exhibit less fluorescence quenching when conjugated to a substance, possess absorption and emission spectra that closely match those of their nonfluorinated analogs, and also exhibit higher quantum yields than their nonfluorinated analogs.