Tumour necrosis factor superfamily member 11 (TNFSF11) gene, that codes for receptor activator of nuclear factor-kappa B ligand, is one of the candidate genes for the genetic susceptibility to osteoporosis. As variations in the TNFSF11 gene promoter could alter its expression, the aim of the study was to evaluate the functional influence of three polymorphisms in the promoter and to investigate their association with bone mineral density (BMD) and biochemical markers in postmenopausal women. A total of 404 postmenopausal women were genotyped for the presence of TNFSF11 gene promoter polymorphisms -290C>T, -643C>T and -693G>C. Two common haplotypes, CCG and TTC, which occur in 44.3 and 49.3% of subjects respectively, were subjected to functional analysis. Amplified fragments were cloned into pGL3-basic reporter plasmid, which was co-transfected with pRL-TK plasmid into HEK293 cells. Dual luciferase reporter assay was performed. BMD and biochemical markers were measured. Reporter gene analysis showed significantly higher luciferase activity in CCG than in TTC haplotype (P=0.018). Both showed association with lumbar spine BMD (BMD-ls; P=0.005 and 0.007 for TTC and CCG respectively), whereas in femoral neck there was no association with BMD. In postmenopausal osteoporosis, association with BMD-Is was established in -290C>T, -643C>T and -693G>C (P values: 0.001, 0.041 and 0.013 respectively). Association with femoral neck BMD was shown in -693G>C (P=0.049). No association was found with biochemical markers in any of the groups. Our results suggest that in postmenopausal osteoporosis, TNFSF11 gene promoter polymorphisms -290C > T, -643C > T and -693G > C play a functional role in the genetic regulation of BMD.