Cavity-enhanced photothermal spectroscopy has been applied to perform ultrasensitive absorption measurements on thin metallic and high-reflectivity dielectric films. The novel method can be employed to determine minute surface-specific absorbances of alpha in the range of a few parts in 10(6) and has high sensitivity since the sample is placed inside a resonant optical cavity. Spatial-, spectral-, and time-resolved measurements were carried out. Laser surface heating calculations have been performed and can be evaluated to yield the thermal diffusivity of the thin films with a resolution at the level of a few micrometers.