OBJECTIVE: Task-specific body-weight-supported treadmill therapy improves walking performance in children with central gait impairment. The aim of the study was to investigate the effect of robotic-assisted treadmill therapy on standing and walking performance in children and adolescents with cerebral palsy and to determine parameters influencing outcome. METHODS: 20 Patients (mean age 11.0 ± 5.1, 10 males and 10 females) with cerebral palsy underwent 12 sessions of robotic-assisted treadmill therapy using the driven gait orthosis Lokomat. Outcome measures were the dimensions D (standing) and E (walking) of the Gross Motor Function Measure (GMFM). RESULTS: Significant improvements in dimension D by 5.9% (± 5.2, p=0.001) and dimension E by 5.3% (± 5.6, p<0.001) of the GMFM were achieved. Improvements in the GMFM D and E were significantly greater in the mildly affected cohort (GMFCS I and II) compared to the more severely affected cohort (GMFCS III and IV). Improvement of the dimension E but not of D correlated positively with the total distance and time walked during the trial (r(s)=0.748, p<0.001). CONCLUSIONS: Children and adolescents with bilateral spastic cerebral palsy showed improvements in the functional tasks of standing and walking after a 3-week trial of robotic-assisted treadmill therapy. The severity of motor impairment affects the amount of the achieved improvement.