High-pressure phase behavior is obtained for CO2 + pentyl acrylate systems at ( 313.15, 333.15, 353.15, 373.15, and 393.15) K and pressures up to 16.8 MPa and for CO2 + pentyl methacrylate systems at ( 313.15, 333.15, 353.15, 373.15, and 393.15) K and pressures up to 17.4 MPa. The solubility of monomers for the CO2 + pentyl acrylate and CO2 + pentyl methacrylate systems increase as the temperature increases at constant pressure. The CO2 + pentyl acrylate and CO2 + pentyl methacrylate systems exhibit type-I phase behavior. The experimental results for CO2 + pentyl acrylate and CO2 + pentyl methacrylate systems were correlated with the Peng-Robinson equation of state using a van der Waals one-fluid mixing rule including two adjustable parameters. A good fit of the data was obtained with the Peng-Robinson equation for CO2 + pentyl acrylate and CO2 + pentyl methacrylate systems. Critical constants ( P-c, T-c, and omega) were predicted with the Joback method and the Lee-Kesler method.