The feasibility study of preparing activated carbon from durian peels by physical activation was investigated. Pyrolysis conditions were studied: durian peels were pyrolysed under either nitrogen or vacuum atmosphere, followed by activation process with carbon dioxide (CO2) at a flow rate of 300 mm3 min-1 for 1 hour. In addition, the influence of chemical treatment after the synthesis on the properties of activated carbon was investigated. The results showed that characteristics of activated carbon produced from durian peels under vacuum conditions are better than those under nitrogen atmosphere. The activated carbon prepared from vacuum pyrolysis provided higher specific surface area and pore volume, and better adsorption of iodine and methylene blue than that from nitrogen atmosphere. Treatment of activated carbon synthesised from both pyrolysis conditions with acid solution (2 M hydrochloric solution) increased specific surface area, pore volume, and adsorption of iodine and methylene blue. The IR spectrum showed that acid treatment unchanged the functional groups of the activated carbon. Instead, pore volume and surface area were increased due to the removal of impurities by the acid treatment.