Zeolitic pores are known to be regular in terms of their shape as well as their size. Since their sizes are in the order of nano meter, the adsorbed molecules should experience the overlapping of adsorption potential field in the pores. Therefore, even adsorbed molecules due to weak van der Waals interaction behave specifically in zeolitic pores and exhibit rather large interaction energy. Pore size regularity results into the molecular sieve effect of zeolites, which causes peculiar catalytic behavior of zeolites. Zeolitic charge unbalance, which originates from the co-existence of metal atoms with different valences, is also the cause of specific adsorption and catalytic behavior. Adsorption behavior of molecules in/on zeolitic nano-scale pores as well as the nature of active adsorption sites of zeolitic surfaces is described. In particular, adsorption behavior is emphasized from the energetic point of view.