The evaluation of small-pore molecular sieves as catalysts for the conversion of methanol to light olefins (MTO) has shown that SAPO-34 exhibits the best performance based on catalyst life, selectivity to C 2 -C 4 olefins, minimum paraffinic and aromatic byproducts and catalyst stability and regenerability. This paper focuses on the catalyst characteristics which have been shown to influence performance, i.e. shape selectivity, acid site strength, acid site density, particle size and Si content. Of the process conditions, the temperature and feed dilution influence performance by affecting the selectivity.