AlPO-34 and SAPO-34 molecular sieves with different silicon content have been synthesized using a hydrothermal system in presence of tetraethylammonium hydroxide (TEAOH) and evaluated as catalysts for the transformation of methanol to short chain olefins. The results showed that SAPO-34 materials prepared with medium-high silicon concentration in the framework present quite similar silicon environment distributions and, when it is so, the key factor to obtain materials with improved catalytic performance is the crystallite size. (C) 2013 Elsevier B.V. All rights reserved.