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The kinetics of the reactions involved in the conversion of methanol to light olefins over SAPO-34, including deactivation caused by coke deposition, has been studied in an oscillating microbalance reactor between 673 and 823 K, space velocities from 50 to 2000 g/gcat,h and methanol partial pressures from 7 to 83 kPa. The proposed reaction network involves dimethyl ether as an unstable primary product, all the olefins formed in parallel as secondary products, and the paraffins formed from further reactions of olefins as stable tertiary products. The selectivity to ethene increased with increasing coke content and temperature. A kinetic model including the deactivating effect due to coke deposition has been developed to properly simulate the changes in activity and selectivity with the coke content. A linear dependency between the coke content and the reaction rate gave the best representation of the experimental data.