Performance characteristics of fuels, such as storage stability and lubricity, are determined mainly by the polar species of the fuel, among them the alkylated phenols. Here, we analyze gas oil and diesel samples, which have been successively desulfurized with different methods, and compare the phenol content and the phenol alkylation pattern of these materials. Because phenols occur in the low parts per million range in the fuel, very sensitive and selective analytical methods are needed for their determination. A derivatization of phenols to ferrocene esters followed by analysis by gas chromatography with both atomic emission detection (iron emission) and mass spectrometric detection is used in this work. Individual concentrations of smaller phenols with up to three substituent carbon atoms and sum parameters were determined. The classical hydrodesulfurization was found to lower the phenol content more drastically than the adsorptive desulfurization. Especially the larger alkylphenols are removed nearly completely during hydrodesulfurization, while they are almost unaffected by adsorptive desulfurization on a Ni/NiO sorbent.