The vibrational overtone spectra of gaseous cycloheptatriene chromium tricarbonyl (CHTCT) and benzene chromium tricarbonyl (BCT) were recorded at the third overtone region using photoacoustic spectroscopy and compared to the spectra of the nonbonded ligands, cycloheptatriene (CHT) and benzene. Analysis of the spectra leads to the conclusion that the metal-ligand bonding lengthens the CH bond by 0.007 Angstrom in the cycloheptatriene complex and by 0.003 Angstrom in the benzene complex. The spectrum of BCT exhibits an additional transition which is absent in the spectrum of free benzene. The experimental peaks are assigned to the pure CH overtones and combination bands. The structural information obtained from the spectra is discussed and compared to the results of gas-phase electron diffraction and microwave spectroscopic studies. Analysis of experimental data indicates that mu 6-bonding is more favorable for cycloheptatriene chromium tricarbonyl.