The hydrothermal stability and the acidity of mesoporous MCM-41 materials are strongly related with their aluminium content. In this work, the influence of the concentration of Al on the textural and acidic properties of MCM-41, as well as on its role as tobacco additive for reducing the toxicity of the smoke generated in the smoking process has been studied. The results obtained show that the material with an intermediate content of aluminium presents acceptable hydrothermal stability, and higher values for the decrease of the yields of CO, CO2, and the condensed and non-condensed products, thus showing the best results from the point of view of reducing the toxicity associated with the generation of toxic and carcinogenic compounds in tobacco smoke. (C) 2011 Elsevier B.V. All rights reserved.