A systematic investigation of reactions of dialkoxyphosphoryl-(thiophosphoryl)sulfenyl chlorides with a wide range of unsaturated organic and elementoorganic compounds such as alkenes, alkynes, dienes, alkenylsilanes and -silatranes, alkenylstannanes, unsaturated phosphonates, unsaturated carboxylic acid derivaties, etc. has been performed. By means of a comparative analysis of the reactivity of phosphoryl- and organylsulfenyl chlorides in similar processes, the principal factors controlling the regiochemistry and the mechanism of the chlorothiophosphorylation of unsaturated systems as well as the character of unconventional AdEreactions have been identified.