Laser optical response of NiO nanostructered films doped with oxidized silver nanoparticles in spectral range of 633-700 nm under the action of carbon monoxide has been revealed. Increased sensitivity of laser induced optical response to carbon monoxide has been demonstrated by micro and nanostructured NiO films modified with silver oxidized nanoparticles. Absorption and diffuse reflection spectra data of composites were used to determine compounds of the composite (Ag2O, NiO, Ag). The sensitivity of the gas action and its dependence on the film microstructure are shown and discussed.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.