The effect of Co content on the catalytic activity of CoSiBEA zeolites in the selective catalytic reduction (SCR) of NO with ethanol is investigated. The Co(x)SiBEA zeolites (x = 0.3, 0.7, 3.6 and 6.75 Co wt.%) are prepared by a two-step postsynthesis method which allows to control the introduction of cobalt into zeolite and thus to obtain catalysts with specific Co sites. The nature of the active sites is characterized by XRD, diffuse reflectance UV-vis, H-2-TPR and XPS. The catalytic activity of CoSiBEA strongly depends on the nature and environment of Co species. Zeolites with isolated lattice tetrahedral Co(II) (Co(0.3)SiBEA and Co(0.7)SiBEA samples) are active in SCR of NO with ethanol with selectivity toward N-2 exceeding 85% for NO conversion from 20 to 70%. When additional isolated extra-lattice octahedral Co(II) species appear (Co(3.6)SiBEA sample), the full oxidation of ethanol by dioxygen becomes a very important reaction pathway. In presence of additional cobalt oxides (Co(6.75)SiBEA sample), the activity and selectivity toward N2 substantially change and full oxidation of ethanol to CO2 is the main reaction pathway and full NO oxidation also takes place in the temperature range 550-775 K. The lack of correlation between the activity in SCR of NO with ethanol and NO oxidation to NO2 suggests that the two reactions are more competitive than sequential. (c) 2007 Elsevier B.V. All rights reserved.