Gas phase reactions of CFx (x=1-3) radicals and F atoms in an electron cyclotron resonance (ECR) downstream plasma have been investigated at 300 W and a CHF3 pressure of 0.4 Pa by adding H-2 to CHF3. The behaviors of CFx radical densities were measured using infrared diode laser absorption spectroscopy, while F atom density was estimated with actinometry. Furthermore, the composition of fluorocarbon films deposited on the chamber walls in the CHF3/H-2 ECR plasma has been investigated with x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy On the basis of measurement results, the correlation between the characteristics of fluorocarbon films and the behaviors of radicals in the plasma has been investigated. The CF radical density was found to be changed by the variation of the composition, in particular F/C ratio, of the films deposited on the chamber walls. Under the same conditions as the measurements of radical densities, the deposition rates of fluorocarbon films formed on the substrate set in the downstream plasma region were measured. The behavior of CF radical density followed the deposition rates, which suggested that the CF radical played an important role for the formation of carbon-rich fluorocarbon films in the CHF3/H-2 ECR plasma.