Cavity ring-down spectroscopy and pressure ramp measurements have been used to determine the extinction coefficients of CO2 in the deep-ultraviolet wavelength region, between 198 and 270 nm. The observed optical extinction confirms that there is a clear absorption onset of CO2 in the deep-UV wavelength region. This onset has been reported previously around 205 nm. The new set of measurements presented here shows that the onset actually starts at higher energy, around 202 nm. For longer wavelengths it is found that the optical extinction demonstrates a 1/lambda(4) like behavior, as typical for Rayleigh scattering. (C) 2008 Elsevier B.V. All rights reserved.