Lean exhausts aftertreatment has been the subject of numerous investigations due to ever stringent regulations on pollutants emissions such as that of NOx. Among aftertreatment technologies, the selective catalytic reduction of NOx by the hydrocarbons (HC-SCR) has been studied intensively, in particular by using Ag/Al2O3 materials. The present work highlights that pretreatment of pristine Al2O3 in warm water prior to Ag deposition allows to prepare catalysts of significantly higher (H2-)C3H6-SCR performance compared to conventional Ag/Al2O3 catalysts. In addition, NOx-TPD-C3H6-SCR structure-activity correlations indicate that optimum composition of the Ag/Al2O3 catalysts can be improved by about 50% in terms of Ag content for the first time. Unprecedented indepth NMR investigations allow for the identification of the alumina sites of importance in the anchoring of Ag. These sites are μ1-OH groups located near the (100)/(110)l edge and then near the (110)b/(100) edge of Al2O3 crystallites and bonded to octahedrally coordinated Al species.