Dissociation constants of selected carboxylic acids in aqueous and organic solvents were calculated at quantum chemical level. We considered cases in which trace quantities of water may be present, as well as cases in which water was entirely absent. In the latter cases, alternative proton acceptors need to be considered. For aqueous solvent, short-range solvation effects are considered by adding explicit water molecules as the first solvent shell. In the absence of water, corresponding organic solvents are used directly as the proton acceptors and the resulted pK(a) are quite comparable to those obtained from previous case of aqueous solvent. (C) 2014 Elsevier B.V. All rights reserved.