Recently, we have shown MCM-22 zeolite as a potential membrane material candidate for hydrogen separation. For hydrogen separation or ultimately integration of hydrogen permselective membranes into membrane reactors for hydrogen production, long-term hydrothermal stability of the membrane is of vital importance. To shed light on the effect of steam on the structural changes of MWW, MCM-22 and its siliceous form (ITQ-1) were exposed to a mixture of steam and nitrogen at relevant conditions to steam methane reforming and water-gas-shift reactions. Behavior of these materials was monitored every 21 days for a total of 84 days using XRD, SEM, TEM and NMR analyses. We will discuss zeolite structural changes as the result of this treatment.