The cetane number (CN) is a measure of the ignition quality of a fuel for compression-ignition engines according to the self-ignition delay. If the CN of a fuel is too low, chemical compounds known as CN. improvers may be added to increase both the CN and performance of the fuel. The addition of CN improvers is dependent upon the detailed properties of the particular fuel. While many fuel properties are important for design, the vapor liquid equilibrium, as described by volatility, is very sensitive to composition. In this work, we measured blends of diesel fuel with the following CN improvers: amyl nitrate, isoamyl nitrate, isoamyl nitrite, 2-ethylhexyl nitrate, and the multi-component CN improver PM-1, in diesel fuel by use of the advanced distillation curve (ADC) method to determine the amount of CN improver in the various distillate volume fractions. Tracking the CN improver throughout the volatility profile of diesel fuels provides valuable information for determining structural property relationships, and moreover, it provides the basis for the development of equations of state that can describe the thermodynamic properties of these complex mixtures, with specific attention paid to additives. We have found that the addition of CN improvers significantly decreases the temperature at which boiling begins and that the majority of the CN improver is thermolytically degraded before the first drop can be collected. These observations are supported by low-pressure ADC, where the CN improver was found in fractions up to 30%. These results have implications in the prediction of thermophysical properties of diesel fuel with CN improvers.