Purpose: to quantify the relationship between individual osteophytic size and measured bone mineral density (BMD) of the lumbar spine by dual x-ray absorptiometry (DXA). Further, to evaluate the possible consequences of this relationship for the management of DXA measurements in postmenopausal patients. Material and Methods: in 142 postmenopausal women (mean age 61.8±8.9 years), plain radiographs of the lumbar spine were evaluated and graded according to evidence and size of osteophytes. the BMD (g/cm2) and Z-score (deviation of BMD from an age-matched population, %) of each vertebral body was determined by DXA. the effects of the individual osteophytic size on BMD measurements were analyzed by using analysis of variance followed by a multiple test procedure. Results: the presence of osteophytes resulted in a significant increase in BMD of L1 through L4. the increase in relation to an osteophytic size of about 10 mm was: in L1 5.7%, in L2 6.8%, in L3 4.4% and in L4 3.5%. Increases were significantly higher for an osteophytic size of 10–20 mm (L1 23.1%, L2 13.0%, L3 13.4%, and L4 16.3%) and of >20 mm (L1 21.4%, L2 22.4%, L3 21.1% and L4 4.1%). Conclusion: Our results indicate a nonlinear increase of measured BMD with increasing osteophytic size. These effects should be considered in routine examination and patient management.