Application of the Domenicano et al. method of estimating group electronegativity from angular geometry of the ring in monosubstituted benzene derivatives allowed us to find how the electronegativity of OH/O- groups in H-bonded complexes of phenol and phenolate depends on the nature and strength of H-bond. For complexes in which the OH group is only proton donating in the H-bond, a linear dependence of the estimated electronegativity on (OO)-O-...(N) interatomic distance was found for experimental (CSD base retrieved) data. The following rule is observed: the weaker the H-bond is, the more electronegative the OH group is. If apart from this kind of interaction the oxygen is proton accepting, then an increase of electronegativity is observed. Modeling (B3LYP/6-311+G**) the variation of the strength of the H-bond by the fluoride anion approaching the OH leads to qualitatively the same picture as the scatter plots for experimental data.