SAPO-40 is a highly active and thermally stable cracking catalyst. A comparison with LZY-82 and SAPO-37 in n-octane cracking shows that after pretreatment at around 800 degrees C and above it is more active than LZY-82. Upon pretreatment at increasing temperature its hydrogen transfer activity decreases while that of SAPO-37 increases. The results are related to the unusually thin SAPO-40 crystals and to the distribution of silicon atoms in the framework.