The influence of UV light absorption by hot CO 2 and H 2 O is evaluated for laser-induced fluorescence (LIF) measurements of NO in high-pressure combustors. UV lasers are ubiquitously used to measure LIF from species like NO, OH, HCO, and O 2 , as well as Raman and Rayleigh scattering in combusting environments. However, attenuation of the laser probe and/or signal by optical absorption from major combustion species is seldom considered. In this paper, we show that neglecting UV attenuation by major product species like CO 2 may lead to large errors in combustion measurements. Absorption cross sections between 190 and 320 nm are measured in shock-heated CO 2 and H 2 O at temperatures ranging from 900 to 3050 K. The absorption cross section of CO 2 has strong temperature dependence and increases by 4 orders of magnitude at 193 nm between 300 and 2000 K. The measured temperature-dependentabsorption spectra for CO 2 and H 2 O are fit to an empirical function to provide a tool for facile assessment of potential errors and quantitative corrections for UV combustion diagnostics. LIF measurements of NO in a highpressure burner and an internal combustion engine are adjusted for CO 2 and H 2 O absorption to demonstrate the importance of these corrections.