This work reports the influence of the comonomer content on the permeation of oxygen in metallocenic polyolefins. These polyolefins are ethylene-1-hexene copolymers with different content of comonomer, and the corresponding homopolymer. It is found that the diffusion and permeability coefficients increase with the temperature and comonomer content, and therefore with the decreasing of crystalline fraction. Moreover, the sorption depends mainly on the fraction of amorphous phase; in fact, the specific sorption, normalized to the crystallinity of the sample, is constant in the interval of crystallinity studied. The permeability characteristics of the films are interpreted in terms of the free volume theory.