The vibrational spectra of trans-p-coumaric acid (pCA) and syringic acid (SA) are discussed. The spectral fingerprints of the organic acids observed in the infrared and Raman spectra are assigned to fundamental vibrational wavenumbers supported by quantum chemical computations. The average surface-enhanced Raman scattering spectra of both acids have been obtained on silver colloidal solutions and the interpretation of the spectra is presented based on complementary Raman spectra and computational results for the silver salts. Copyright (C) 2009 John Wiley & Sons, Ltd.