Broad review on pore structure models. Different types of pores and porous media are described. A very imporant characteristic is pore connectivity, which also depends on where the molecules adsorb. Discrete and continuum models. From page 26 on some personal reflections in which fractals play a major role. Tomographical techniques are useful for characterization. Models for amorphous media including the percolation theory. Chapter 3 delas with models of disordered porous media for the description of mass transport. Finally, the review on pore structures and models for other systems including rocks, clays/soil, and cements.