In order to determine the viscosity of liquid and gaseous chlorofluorocarbons, various experimental approaches and graphs have been developed, but they had a limited use. In this study, the viscosity of chlorofluorocarbons and hydrocarbon mixtures has been determined by applying a reliable model based n the Peng-Robinson cubic equation of state and the mixing rule for hydrocarbon mixtures. Finally, the Fminsearch algorithm has been used to optimize the result of 531 data points including 451 points for pure chlorofluorocarbons (167 points for saturated liquid chlorofluorocarbons, 284 points for unsaturated gaseous chlorofluorocarbons (R13, R32) and 80 points for binary mixtures. In this study, a large chlorofluorocarbon data set obtained for a wide pressure (3237-5805 kPa), and temperature (301.84-487.40 K) ranges has been used. The results show a similarity between the experimental data and the model results. For 17 pure chlorofluorocarbons considered in this study, the calculated average absolute deviation is 1.92%, and the average relative error for four two-component hydrocarbon mixtures is 5.28%. A difference between the predicted and the experimental viscosity for R13 and R32 was mainly 0.1. In general, the analyzed model is accurate and does not require the bulk density that represents its main advantage.