Hydrocarbon emissions of a vehicle during cold start must be reduced to meet stringent emission regulations. In this paper, three honeycomb hydrocarbon adsorbers were prepared by using H-ZSM-5 and materials of conventional three-way catalysts. A new method was proposed, namely, temperature-programmed adsorption, to evaluate simultaneously the performance of adsorption and conversion of decane on the adsorber. The adsorption amount and conversion of decane on the adsorbers were varied with the Si/Al ratio of H-ZSM-5 and the loading amount of precious metal TM) and hydrothermal aging. There was a trade-off between the adsorption amount and the conversion. The coexistent gas effect on the adsorption of decane on the two-cycle-aged adsorber seemed to increase in the order of CO, NO, O-2, and H2O in the conditions simulated to the emissions of a vehicle. The pore structure at fresh and hydrothermal aged states of the adsorbers was observed by using nitrogen.