We discuss our own studies of molecular adsorption on and inside of single-wall carbon nanotubes in the broader context of important theoretical and experimental developments in the field. We show that adsorption in the nanotube interior sites as well as in the groove and exterior sites may be resolved by various experimental methods. In addition, the changes that the adsorbate phases undergo due to confinement in the nanotube interior are discussed, particularly focusing on confined molecules of water, alkanes, and an alkene. Attention is also devoted to the use of oxidizing agents such as ozone to open the ends and walls of nanotubes for interior adsorption.