The effect of changes in the molecular structure of 3,3(.)- and 4,4(.)-disubstituted azobenzenes, caused by the photoisomerization process, on both, capabilities of these compounds to form monolayers on a water surface and the behavior of their monolayers, are described and discussed. It has been found that their Z-isomers form monolayer whereas the E-isomers do not. Moreover it has been found also that the peculiar isomerization behavior of 3,3(.)-disubstituted azobenzenes, whose rodshape form is preserved during the photoisomerization process, result in a different behavior of the monolayers of these compounds from the ones of 4,4(.)-disubstituted azobenzenes. The bent form of the Z-isomers of 4,4(.)-disubstituted azobenzenes that favors the interaction of the azo polar group with a water surface has been pointed out as the origin of the remarkable stability of their monolayers. Finally, the results of this study have been successfully used for revealing the mechanism of so-called light-induced anchoring transition of nematics.