The aim of this study was to evaluate how wearing one or two orthoses influence the gait parameters in children with hemiplegia. Four children with hemiplegic cerebral palsy participated in the study. Patients were from 3 to 7 years old; one girl and three boys; one patient with right side hemiplegia, three patients with left side hemiplegia. Patients underwent the VICON MX system gait analysis three times (sessions): one with bare feet, the other two with shoes and orthoses: one with orthoses used unilaterally on palsied limb, one with orthoses used bilaterally. The following gait parameters were analyzed: velocity, cadence, pelvis tilt, range of pelvic movement in sagittal plane, separately for affected and non-affected side: step length, stance time (as a percentage of the gait cycle), range of hip movement in sagittal plane, knee flexion at initial contact, maximum knee flexion in swing phase. Results of the study showed which and how many gait parameters changed while wearing one in comparison with two orthoses. The results did not give a clear indication which condition is better: wearing one or two orthoses, however they suggest that when the orthotic devices are considered for patients with hemiplegic cerebral palsy, the objective, instrumented gait analysis can be used to take the best decision whether one or two orthoses should be prescribed.