Background/Aims: The present analyses intend to clarify if gender and puberty modify the relationship between bone development (modeling and remodeling) and fat mass at the forearm. Methods: Data were collected from participants (139 males, 157 females, age = 5–19 years) of the Dortmund Nutritional and Anthropometric Longitudinally Designed study in a cross-sectional investigation. The main outcome measures were total and trabecular bone mineral density (BMDtot and BMDtrab), strength strain index (SSI) and parameters associated with modeling (cortical area, CA; periosteal circumference, CP) and remodeling (cortical bone mineral density, BMDcort, endosteal circumference, CE) were analyzed in their relationship to cross-sectional fat (FA) and muscle area (MA) at the forearm. Results: BMDtot was correlated with FA in pubertal males (r = –0.25). BMDtrab was contrarily predicted by FA in pubertal males and females (r = –0.28 vs. 0.31). FA was correlated with BMDcort (r = –0.32) and CE (r = 0.26) in pubertal females. MA was positively correlated with CA, CP and SSI. Conclusions: Modeling and bone strength were primarily predicted by MA. Markers of remodeling were positively correlated with FA in pubertal females, but not in prepubertal individuals and pubertal males. Therefore, gender and puberty modify the relationship between FA and bone development.