We report the observation of wavelength-dependence in the early phases of the laser ablation of chemical vapor deposited (CVD) diamond films. The measurements were made with 3–4 μm infrared radiation from the Vanderbilt Free-Electron Laser (FEL), the brightest tunable mid-infrared FEL in the world. Though we do not propose any specific mechanism for the ablation, the C-H bond-stretching mode at 3.47 μm is clearly important in the early stagesof the damage process, as evidenced by a sharp drop in the ablation threshold near 3.47 μm.The ablation damage threshold was determined by directing a single FEL pulse at the sampleand measuring the diameter of the resulting hole using a scanning electron microscope (SEM).This measurement was repeated for several pulse intensities. The damage threshold was defined as the extrapolation to zero hole diameter. We also looked at the desorption productsusing a time-of-flight spectrometer and a quadrupole mass analyzer. C2 is the dominant desorbed species. Visible light emission was monitored with a monochromator and photodetector.