This study involves the preparation of a number of polymer inclusion membranes (PIMs) using a variety of commercial solvent extraction reagents immobilized in cellulose triacetate (CTA), cellulose acetate, poly(vinyl chloride) (PVC), PVC co-polymerized with vinyl alcohol and vinyl acetate, and carboxylated PVC. The influence of the molecular structure and physicochemical properties of the extractants studied on their ability to form homogeneous, flexible and mechanical strong PIMs are discussed. The physicochemical properties found to be of most importance in this respect are the extractant's lipophilicity, hydrogen bonding capacity, ability to participate in dipole-dipole interactions and its liquid aggregate state at room temperature.