Calculated geometries are presented for five aromatic N-sulfinylamines, R-N=S=O, All carry at least one hydrogen atom on the aromatic ring ortho to the NSO substituent, and all show a preference for a planar isomer in which the substituent's oxygen atom is oriented toward an ortho hydrogen. All these isomers exhibit a shortening of the corresponding C-H bond. Using the quantum theory of atoms in molecules (AIM), it can be shown that a C-H . . .O bonding interaction exists that meets all the characteristics of an anti-hydrogen bond.