This study investigated the relative contribution of fat mass and lean mass to bone mineral density (BMD) in young and premenopausal healthy Chinese women. The study was performed in 282 young and premenopausal healthy women with regular menstrual cycles. The BMD at lumbar spine (L2-L4), total hip and total body, together with fat mass and lean mass were assessed by dual-energy X-ray absorptiometry (DXA); body height, weight, waist and hip circumference were also measured, and body mass index (BMI) and waist-hip ratio were calculated. Fat mass was a major determinant for BMI, BMI and lean mass were positively related to L2-L4, total hip and total body bone density ( P<0.001 for all), lean mass was the only independent factor contributing to BMD at L2-L4 (standardized coefficient beta=0.282, P<0.001), total hip (beta=0.336, P<0.001) and total body (beta=0.361, P<0.001) in multiple stepwise regression analysis. The correlation between BMI and BMD was improved after adjustment for fat mass, while decreased or even lost when lean mass was adjusted. These data suggested that in the Chinese population, lean mass is an important factor determining BMD in young and premenopausal women.