The aim of this study was to analyze the selected single-nucleotide polymorphisms (SNPs) of the OPG (TNFRSF11B) gene, rs3102735 (−163A>G), rs3134070 (−245T>G), rs207361 (−950T>C), rs7844539 (6890A>C), and rs2073618 (1181G>C), in the development of osteoporosis and osteopenia in postmenopausal women. This evidence concerns the gene TNFRSF11B and Osteopenia.