Group contribution methods are commonly used for the estimation of Henry's law constants when no experimental data are available. However, these methods are of limited accuracy for complex molecules in which proximity effects, that is the effects on one group by neighboring groups on the same molecule, are important. A recently developed multipole correction method accounts the variation of the charge and dipole moment of a functional group when it is located in different molecules or in different positions oil the same molecule. Here we use a single-molecule quantum mechanics calculation to compute the electrostatics of each functional group, which is then used to correct a group contribution method for the prediction of the Henry's law constant (H) of compounds in water for the effects of proximate strong intramolecular functional groups. This new hybrid quantum mechanics-group contribution model results in a root-mean-square deviation of 0.34 in log(10)H for a total of 395 compounds, which is more accurate then the bond (0.43) and group (0.52) contribution methods of Meylan and Howard that have a greater number of parameters.