The properties and the organization of poly (D, L-lactic acid) monolayers spread at the air/water interface were shown to be dramatically dependent on whether these monolayers have been spread from a good or a bad solvent. Whereas a good solvent, such as chloroform, favored the deployment of polymer chains from their coiled structure in solution to the unfolded structure, a bad solvent, as exemplified by acetone, enhanced strong intersegment interactions resulting in the formation of microdomains capable of respreading and favored adhesion of the polymer monolayer to water. Independently carried out experiments with monolayers of ester derivatives of hyaluronic acid demonstrated that the nature of a chemical group substituted on the glucuronic acid moieties of the polymer can considerably influence surface properties of these monolayers. Thus, if monolayers of the ethyl ester derivative were shown to be rather compressible, those of the benzyl ester derivative were more rigid and, relative to the ethyl ester derivative, they exhibited increased adhesion to the water subphase within a wide range of areas. It has been shown that the van Oss-Chaudhury-Good theoretical approach applied to the calculation of interfacial free energies of these monolayers with water, obtained from the contact angle data on their Langmuir-Blodgett films, was perfectly adapted to explain the observed differences in their adhesion properties.