Since single nucleotide polymorphisms (SNPs) may modify gene function or can be used as genetic markers to detect nearby disease-causing variants through association or linkage studies, we sought to evaluate the association of six potentially functional SNPs (i.e., RAD51 −135G>C/rs1801320, −172G>T/rs1801321, XRCC2 4234G>C/rs3218384, R188H/rs3218536 G>A, XRCC3 T241M/rs861539, and NBN E185Q/rs1805794) of genes involved in HR pathway with radiation pneumonitis (RP) and overall survival (OS) of NSCLC patients treated with definitive radio(chemo)therapy in the present study. This evidence concerns the gene NBN and radiation pneumonitis.