Pseudohalogen-containing compounds have attracted significant interest among nonmetal chemists and theorists, not only owing to their potential use in various fields but also due to difficulties in their experimental preparation and characterization. Since its introduction in 1925, the pseudohalide principle has been used extensively and, therefore, a remarkable progress has been made in the experimental and theoretical research on the compounds of this kind. In this work, we review studies on structural investigations and theoretical characterizations of several pseudohalide-containing compounds in order to contribute to better understanding of the chemistry of many such species.