We examined the relationships between serum levels of intact parathyroid hormone (PTH) and alkaline phosphatase (ALP) versus bone mineral density (BMD) at the lumbar spine and radius in terms of their preoperative values and of their annual percentage and net changes after parathyroidectomy (PTX) in 44 Japanese patients (14 men and 30 women) with primary hyperparathyroidism (pHPT). Lumbar and radial BMD values were measured by dual energy X-ray absorptiometry and single photon absorptiometry and were used for evaluating the cancellous and cortical bone mass, respectively. Age- and sex-adjusted value (Z-score) of the radial BMD was significantly lower than that of the lumbar BMD before and after PTX (P<0.05). In preoperative patients, serum levels of both intact PTH and ALP were significantly and negatively correlated with Z-score of the radial BMD (P<0.05 and P<0.001, respectively), but not with that of the lumbar BMD. After PTX, serum levels of calcium, phosphorus, ALP, and PTH became normal, and both lumbar and radial BMD values markedly increased over 1 year, with percentage changes of 12.2±1.4% and 11.6±1.6%, respectively, which were larger than those in any other Caucasian study previously documented. Even in patients without osteopenia (Z-score of BMD≥0), lumbar and radial BMD values increased considerably after the operation (9.6±1.9% and 6.7±1.4%, respectively). Annual percentage and net changes in lumbar BMD were significantly and negatively correlated with those in ALP with high correlation coefficients, but those in radial BMD were correlated only with the annual net change in ALP but not with the percentage change. No significant correlations were observed between annual changes in either lumbar or radial BMD and those in intact PTH. Taken together, this study shows that PTX causes dramatic improvements in both the cancellous and cortical bone mass in Japanese pHPT patients regardless of the severity of their osteopenia, and suggests that the cancellous and cortical bones react differently to a preoperative endogenous PTH excess and a high bone turnover rate as well as to the postoperative normalization of a bone turnover rate in the patients.