Aim/Hypothesis. To examine whether children with DMT1 are less physically fit than healthy children and to assess whether an elevated level of HbA1c was associated with decreased physical fitness among children with diabetes. Methods. The study was conducted using case-control methodology. The cases were 100 children with T1DM, 7–17,9 years. Study subjects underwent a 6MWT, where distance measured, heart rate, and oxygen saturation was recorded. Results. Results of the 6MWT for children with T1DM and controls were 601.3 ± 86.1 meters versus 672.1 ± 60.6 meters, respectively (P < 0.001). The cases were divided into two subgroups, one with HbA1c levels >8% and one with HbA1c <8%. Results for both groups were inferior to the controls (P < 0.001). The posttest pulse rate in all subjects was higher than the pretest pulse rate (P < 0.001). Pulse oxygen levels were lower than controls at the pretest measurement (P < 0.001), and for both cases and controls, pulse oxygen levels decreased after test (P = 0.004). However, the change in oxygen saturation did not differ between the groups (P = 0.332). Conclusions. Children with T1D are less fit than matched controls. The level of HbA1c did not affect the physical fitness of children with T1D.