This paper reports the results of a study on basic adsorption properties of three different zeolitic materials (HZSM5, Silicalite, HY) towards hydrocarbons present at engine exhaust during cold start. Equilibrium isotherm curves at room temperature are presented for three model hydrocarbons (ethylene, isobutene, toluene), considered as representative of the most concentrated compounds detectable at engine start-up. Breakthrough curves, obtained at different temperatures by flow adsorption tests with the selected hydrocarbons, are also discussed. Finally the results of flow adsorption tests performed on the three zeolitic materials at engine exhaust are shown. The aim is to understand how the physico-chemical characteristics of the adsorbent material can affect its trapping capability in adsorbing all the types of hydrocarbons present in the engine exhaust.