Osteoporosis constitutes a major public health concern and its underlying pathogenesis is complex and multifactorial. Although hereditary factors strongly contribute to bone health, behavioural factors can modulate the genetically determined pattern of skeletal modelling and remodelling.The aim of this study was to investigate the effect(s) of behavioural risk factors on osteoporosis in Irish women.Pre- and post-menopausal adult women (n = 189; 44 +/- A 15 years) participated in this cross-sectional study. Demographic, anthropometric and lifestyle data were collected during a single clinic visit. Dietary calcium intake and lifetime physical activity (PA) were assessed for each subject. Lumbar and femoral bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA). Multivariate analysis was used to determine the independent predictors of low BMD.Low BMD was present in 59 % of subjects (42 % pre- and 77 % post-menopausal). Smoking was the strongest behavioural predictor of lumbar and femoral BMD. Age, height, family history, smoking, metabolic (MET) and mechanical (MECH) PA (lifetime) and weight (body mass) accounted for 39 % of the variance in lumbar BMD. Age, height, family history, alcohol consumption, MET and MECH PA (lifetime) and weight accounted for 41 % of the variance in femoral BMD.Prevalence of osteopenia and osteoporosis is high in Irish women and is associated with modifiable risk factors. A clearer focus should be paid to educate Irish women on preventative health behaviours for osteoporosis to curb the prevalence of this disease and the human and fiscal costs associated with it.