Dubinin-Astakhov (D-A) equation is used for determining the micropore volume and surface area of zeolite molecular sieves (ZMS) by using physisorption measurements. Likewise, Dubinin-Radushkevich (D-R) equation is used for the estimation of these parameters for carbon molecular sieves (CMS), and, unlike D-A equation it does not require the estimation of the exponent n. In this paper, surface area and micropore volume of 13X molecular sieves (MS) have been determined by using both D-A and D-R equations. The results by both equations are in very good agreement. Therefore, D-R equation may also be used for estimation of these parameters because its application is simple and easier.