Low-density polyethylene (LDPE) has been investigated with respect to the diffusion of hindered phenol antioxidants added to the polymer matrix. In the study, a simple method was used to measure the diffusion coefficient, with the aid of FTIR spectroscopy without any extraction or refining steps in the analysis. The diffusion coefficient, D, of five phenols containing the same 3(3,5-di-tert-butyl-4-hydroxyphenyl) structure but with different lengths of the hydrocarbon tail were obtained in the temperature range 30-60-degrees-C. The number of carbon atoms in the tail varied between 1 and 18. It was found that the logarithm of D decreased linearly with increasing molecular size. The temperature-dependence of the phenols could be described by an Arrhenius-type relationship. It was found that the activation energy, E(d), increased linearly with increasing molecular size.