A beta zeolite modified by treatment with aluminium ions has been characterized by different techniques, such as XRD, XPS, N-2 adsorption, and TPD of pyridine and acetonitrile. Compared to the parent zeolite, it has shown some differences concerning the local environment of the aluminium atoms and the distribution of the acid sites. The modified zeolite has been tested as catalyst in a model reaction, i.e. the conversion of methanol to hydrocarbons, where it has exhibited higher activity than the parent zeolite.