The capability of atomic tritium to penetrate deep into anhydrous targets of complex composition was examined. Amino acids coated with cetylamine were used as targets. With an increase in the cetylamine layer thickness, the yield of labeled amino acids drastically decreased, whereas the yield of labeled by-products increased. Measurements of the radioactivity of the amino acids allowed evaluation of the capability of cetylamine layers to transmit tritium atoms, which was characterized by gravimetric attenuation coefficients. The attenuation coefficient depends on particular amino acid used as indicator and on the cetylamine layer thickness. The most accurate values of the attenuation factors were obtained from the radioactivity of all the reaction products, taking into account the nonuniformity of cetylamine application onto the target. A decrease in the attenuation coefficient in thick cetylamine coatings was attributed to the open-work (porous) structure of these layers.