The vibrational frequencies of OH and NH groups which form hydrogen bonds to a water molecule are calculated using the complete active space self-consistent field (CASSCF) method and the second order perturbation theory based on the CASSCF reference (CASPT2). As model systems indole(H2O), phenol(H2O), and their corresponding cations are chosen. Furthermore, different isomers of the 3-aminophenol(H2O)(+) and 4-aminophenol(H2O)(+) clusters are considered. For all these clusters IR spectra are known, but the IR spectra of the ionic clusters in the region of the hydrogen-bonded OH and NH groups have not yet been well interpreted. Due to the strong anharmonicity of the OH and NH vibrations it is not possible to predict their frequencies by a simple scaling of harmonic values. By using different active spaces including both pi -orbitals as well as sigma -orbitals it is shown that the vibrational frequencies can be derived from potentials obtained from CASSCF single-point calculations along the OH and NH stretching modes. These vibrations can be regarded as proton-transfer coordinates. The calculated vibrational frequencies are in excellent agreement with the experimental values obtained for the investigated clusters. Furthermore, a strong shift of the OH stretching frequency is predicted by going from phenol(H2O)(+) to aminophenol(H2O)(+) clusters, explaining the completely different IR spectra of the investigated species.