This chapter emphasizes the important effects on chemical, biological, and physical properties of the substitution of hydrogen by fluorine in organic compounds. The properties of a new class of fluorine-containing organic compounds, such as heterocyclic ones, are determined by the peculiar influence of fluorine atoms as substituents. The new, unique properties of fluorine-containing compounds and areas of their practical applications are focused on in the chapter. The reactions of binucleophilic reagents with terminal perfluro-olefins and internal perfluro-olefins as intermediates in the syntheses of heterocyclic compounds are also discussed in the chapter. The introduction of fluorine atoms can lead to substantial increases of biological activity, making wide investigations in the field of fluorine-containing heterocyclic compounds necessary. Reactions of perfluoro-olefins with bidentate nucleophiles in the presence of bases lead to various heterocycles with five-, six-, seven-, and eight-membered rings containing perfluoro-alkyl groups. The synthesis of three-membered heterocycles, containing nitrogen, sulfur, and oxygen atoms are presented in the chapter. The synthesis of four-membered heterocyclic compounds with atoms of V-VI group elements is discussed in the chapter. The methods for the synthesis of five-membered heterocyclic compounds and six-membered heterocycles with one or more heteroatoms are reviewed in the chapter. Seven-membered cycles with many heteroatoms are obtained from internal perfluoro-olefins.