The UV-vis absorption spectra of 1,1,1-trifluoracetylacetone and 1,1,1-trifluoro-3-(2-thenoyl)acetone are studied in water and in aqueous micellar solutions of cationic surfactants forming micelles. In strong acid medium, the presence of micelles does not change the spectra of these trifluoro-diketones; however, in aqueous buffered solutions of acetic acid-acetate, addition of surfactant causes the formation of enolate anions. In strong alkaline medium, or in carbonate-bicarbonate buffer solution, the enolate decomposes. The rate of decomposition is reduced strongly by the presence of cationic micelles. The quantitative treatment of spectral changes measured as a function of pH, in both the absence and presence of surfactants, allows us to determine the keto-enol equilibrium constants, as well as the acidity equilibrium constant of both the enol and keto tautomers. Both 1,1,1-trifluoroacetylacetone and 1,1,1-trifluoro-3-(2-thenoyl)acetone are less than 2% enolized in water. The presence of micelles does not increase the enol content; by contrast, a strong increase of their acidity by approximately two pK(a) units is observed. The enol of these two trifluoro-diketones is more acidic than the keto tautomer, a common observed phenomenon when the enol content is very low.