Aims: The objectives of this study were to investigate relationships of inflammation and adiposity with bone mineral density (BMD) in youth with type 1 diabetes followed prospectively for 18 months. Methods: Participants were youth with type 1 diabetes (n = 136, 8-16.9 years) enrolled in an 18-month behavioral nutrition intervention trial. BMD of the total body, subtotal, lumbar spine, pelvis leg, arm and rib, percent body fat and percent trunk fat (by dual energy x-ray absorptiometry) and C-reactive protein (CRP), a marker of inflammation, were assessed at baseline, 12 and 18 months. Linear mixed-effects models estimated associations of time-varying BMD with time-varying CRP, and with percent body and trunk fat. Results: CRP was inversely associated with BMD of the total body, pelvis and leg (n = 136). Percent body fat was inversely associated with BMD of the total body and pelvis; whereas percent trunk fat was related only to total body BMD. Conclusions: Greater inflammation and adiposity were related to lower BMD in youth with type 1 diabetes. Investigating the impact of inflammation and adiposity on bone turnover markers could provide insights on mechanisms that contribute to this relationship. Published by Elsevier B.V.