Both cw and pulsed photothermal deflection techniques have been applied to make in-situ investigations of laser conditioning of optical coatings. Two different kinds of lasers have been used for the conditioning, namely 488 nm-cw-Ar+ and 1.06 micrometers -10 ns- Nd:YAG. The samples investigated include thermally evaporated TiO2, ZrO2, HfO2, Al2O3, SiO2, MgF2, and ZnS single layers as well as TiO2/SiO2, ZrO2/SiO2, and HfO2/SiO2 HR coatings. While the conditioning effects on the damage thresholds vary from sample to sample and depend on the specific irradiation parameters, a good correlation is observed between the in-situ measured change in absorption and the improvement of the damage resistance. Also presented in this paper are the detection of the change in defect density and thermal conductivity of the irradiated area. The latter, however, is small for most of the samples.