The present research is concerned with the question of why activated carbons that show good adsorption uptake for model diesel sulfur compounds are not effective for real diesel fuels. In this work, the effects of aromatics, O-containing fuel additives, nitrogen compounds, and moisture present in real diesel fuel on adsorption desulfurization (ADS) over a commercial activated carbon (AC-WPH) were investigated. Polyaromatics such as phenanthrene show a significant inhibiting effect on ADS, even at a concentration of less than 1.0 wt %, while monoaromatics such as butylbenzene, even up to 10 wt %, have a negligible effect. The adsorption of different sulfur compounds over AC-WPH can be attributed mainly to the interaction of their conjugated pi electrons with the carbon surface, where the electron-donating methyl groups further enhance the interaction. Trace amounts of O-containing diesel additives, nitrogen compounds, and moisture all have inhibiting effects on adsorptive desulfurization over AC-WPH, which can be attributed partly to hydrogen-bonding interaction between polar groups.