The infrared signature of carbon dioxide clusters of nanometric size is discussed both in the bending (nu(2) mode at 15 mum) and in the asymmetric stretching (nu(3) mode at 4.2 mum) spectral region of the monomer. The carbon dioxide nanoparticles were formed using a capillary tube injection inserted upstream of a uniform supersonic flow of argon generated by a Laval nozzle. The size of the formed clusters was varied by changing the stagnation pressure P-0 of the capillary. The empirical power law connecting P-0 to the number N of monomers per cluster: Nproportional toP(0)(2.2) was verified in this work. The cluster mean size was estimated using a Rayleigh scattering experiment showing the formation of nanometric clusters whose radii are in the range 0.7 nm