Surface-enhanced Raman spectroscopy (SERS) was used to characterise interactions between six tridehy- dropeptides and the silver electrode. Boc-Gly-X-Gly-OMe and Boc-Gly-X-Gly-COOH (X = dehydroalanine ( D Ala), dehydrophenylalanine ( D (Z) Phe and D (E) Phe) were studied in this work. The type of the rigid dehydroamino acid residue and the isomer of D Phe have a strong impact on the adsorption mechanism of the peptides. The respective vibrational assignments were proposed by the analysis of FTIR and FT-Raman spectra of solids enabling the evaluation of SERS spectra. Generally, the most intensive SERS bands relative to those in the bulk-phase spectra are associated with vibrations of the dehydroamino acid moiety, i.e. the C @ C bond and the phenyl ring. Only, in the case of the peptides containing the D Ala and D (Z) Phe residues and ionised carboxylate group, the molecules interact with the silver electrode via the peptide backbone. In most cases of the peptide containing D Phe the aromatic ring is almost perpendicular to the metal surface.