To investigate the nature of nonbonded (SeO)-O-... interactions, three series of 2-substituted benzeneselenenyl derivatives [2-(CHO)C6H4SeX (1), 2-(CH2OH)C6H4SeX, (2), 2-(CH(2)OiPr)C6H4SeX (3); X = Cl, Br, CN, SPh, SeAr, Me] were synthesized. The O-17 NMR absorption observed for O-17-enriched aldehydes 1 appeared upfield relative to benzaldehyde (PhCHO), while the opposite downfield shifts relative to benzyl alcohol (PhCH2OH) were observed for O-17-enriched alcohols 2 and ethers 3. The magnitude of both the upfield and the downfield shifts became larger as the electron-withdrawing ability of a substituent X increased. Quantum chemical calculations at the B3LYP level revealed that for all model compounds the most stable conformer has an intramolecular nonbonded (SeO)-O-... interaction. Thus, the relative O-17 NMR chemical shifts (Deltadelta(o)) for 1-3 would reflect the strengths of the (SeO)-O-... interactions. The natural bond orbital (NBO) analysis demonstrated that the stabilization energy due to an no --> sigma(Se-X)(*) orbital interaction ((ESeO)-O-...) correlates with the (SeO)-O-... atomic distance on a single curve irrespective of the type of the O atom. On the other hand, the atoms in molecules (AIM) analysis showed that the nonbonded (SeO)-O-... interactions can be characterized by the presence of a bond critical point, the total energy density ((HSeO)-O-...) of which decreases with strengthening of the interaction. The results suggested that (SeO)-O-... interactions have a dominant covalent character rather than an electrostatic one.