The stem borer Sesamia nonagrioides (Lefèbvre) is the most important insect pest that attacks maize, Zea mays L., in northwestern Spain. Host plant resistance to this borer was investigated in relation to the cell wall phenylpropanoids content in the pith. Eight inbred lines that differ in resistance were analyzed. Three major simple phenolic acids, p-coumaric, trans-ferulic, and cis-ferulic acids, and three isomers of diferulic acid, 8-5', 8-O-4', and 8-5'b (benzofuran form), were identified. The amount of all these compounds was correlated with the resistance level in the genotypes, with the resistant inbreds having the highest concentrations. The role of these compounds in cell wall fortification and lignification is well-documented, suggesting their possible intervention in S. nonagrioides resistance. Future studies that focus on these compounds could be useful to enhance S. nonagroides resistance.