In this work we have studied the permeability of polymer films that had a core and shell composed by polystyrene and poly (butyl acrylate) in a mass relation of 40 and 60, respectively. Permeability coefficient measurements were made in the Permeation Chamber "Voyager". The permeated gases were nitrogen, oxygen, methane and carbon dioxide at a temperature of 35 °C and pressures of 2 and 4 atmospheres. According to the results, the permeabilities of the films using latex obtained by polymerization in microemulsion were lower compared to those obtained using latex core-shell polymer obtained by emulsion polymerization and this is due to that smaller diameter nanoparticles were obtained by microemulsion polymerization than those obtained by emulsion. Also, a direct relationship between the coefficient of permeability of gases with critical temperatures of the gases was found.