A brief conformational, structural and vibrational study has been performed on the molecular structure of two well known amino acids tyrosine and L-DOPA. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by the Density Functional B3LYP method employing 6-311G(d,p) as the basis set and the vibrational studies were interpreted in terms of potential energy distribution (P.E.D.). The internal coordinates were optimized repeatedly to maximize the P.E.D. contributions. A detailed interpretation of the infrared and Raman spectra of tyrosine and L-DOPA is reported in the present work. The similarities and differences between the vibrational spectra of the two molecules studied have been highlighted. The calculations are in agreement with experiment. The thermodynamic calculations related to the title compounds were also performed at B3LYP/6-311G(d,p) level of theory. The FT-Raman and FT-IR spectra of tyrosine and L-DOPA have been taken from literature