The advantages of using polystyrene as an x‐ray absorber are pointed out. The measured linear absorption coefficient for both commercial rod and high‐purity molded sheet was found to be 4.165±0.008 cm−1for CuK&agr;radiation. The mass absorption coefficient of carbon (&mgr;l/&rgr;) is 4.301±0.009 cm2/g. This value is compared to other published results.