To investigate bone health and body composition in young women with long-duration type 1 diabetes (T1D) in relation to matched controls. Twenty-three Swedish women, age 19.2–27.9 years, with a T1D duration of 10 years or more were recruited from the Swedish National Diabetes Registry (NDR). An age-, gender- and geography-matched control group was recruited. Bone mass and body composition were assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. Data was retrieved from the NDR and SWEDIABKIDS registries. T1D individuals had a mean diabetes duration of 19 years. T1D individuals had reduced lean mass (40.0 ± 6.1 kg vs. 43.9 ± 4.9 kg) and were shorter (1.66 ± 0.06 m vs. 1.71 ± 0.06 m) although comparable BMI. Subjects with T1D had lower muscle area (P = 0.0045). No differences were observed for fractures; physical activity; total, lumbar spine or femur areal bone mineral density. The cortical bone strength strain index was lower for TD1 patients (1875 ± 399 mm³ vs. 2277 ± 332 mm³). In conclusion, young women with long-term diabetes duration showed reduced cortical bone strength, decreased periosteal circumference, endosteal circumference and altered body composition. These factors contribute to the health burden of TD1, which warrants further attention for advancing bone health in women with T1D.