Little is known about the association between vitamin D deficiency and the skeletal phenotypes in primary hyperparathyroidism (PHPT) patients. A low 25-hydroxyvitamin D level was associated with a low bone mineral density and deteriorated hip geometry in women with PHPT in an Asian population where vitamin D deficiency is prevalent. Few studies have examined the effect of vitamin D deficiency on the bone health of primary hyperparathyroidism (PHPT) patients. We investigated the skeletal effects of vitamin D deficiency in 79 PHPT patients by assessing bone mineral density (BMD), the trabecular bone score (TBS), and hip geometry, which were measured using dual-energy X-ray absorptiometry (27 men with median age 60 years [53;69]; 52 postmenopausal women with median age of 57 years [53;67]). Cross-sectional data were collected from subjects enrolled in an ongoing PHPT cohort study at Seoul National University Hospital from March 2008 to December 2015. We classified PHPT patients according to 25-hydroxyvitamin D (25(OH)D) levels (< 20 vs. ae20 ng/ml). After adjusting for age and body mass index, women with vitamin D deficiency had lower BMDs at the lumbar spine (LS) and femur neck (FN) than women who had sufficient levels of vitamin D (LS, 0.903 +/- 0.138 vs. 0.998 +/- 0.184 g/cm(2); FN, 0.715 +/- 0.084 vs. 0.791 +/- 0.113 g/cm(2); P < 0.05). However, the total hip BMD and the TBS were not significantly different between the two groups. In the hip geometry analysis, the cross-sectional area, cross-sectional moment of inertia, and section modulus were also significantly lower in women with vitamin D deficiency than in those without. No significant difference was found in the BMD, TBS, or hip geometry according to 25(OH)D levels in men. Vitamin D deficiency may be associated with a low BMD and deteriorated hip geometry in postmenopausal women with PHPT.