The methods enable the objective gait evaluation of the gait in children with cerebral palsy (CP). One of the indexes used to the analysis is Gillette Gait Index (GGI), complying 16 clinically meaningful kinematic and three-dimensional parameters. The study was conducted with application of the three-dimensional system of gait analysis BTS Smart. Spatial-time parameters of gait and courses of angles of joint of lower limbs were determined on the basis of conducted research. Those parameters were used in estimation of Gillette Gait Index. The analyzed group consisted of 12 cerebral palsy children at the age of 5–13 years. All the children were assessed by the team before and after the botulin injection. The authors present the result of on the base of one of one patient, a girl at the age of 12 with right-sided spastic hemiparesis. The patient was evaluated three-times: before the botulin treatment, then three and six months after botulin injection. The value of the mean antetorsion of the pelvis in the saggital plain is now comparable to the healthy children at the same age. The GGI index improved in both lower extremities, for the right one within 24.14% and for the left one up to 40.69%. The authors regard the results presented above as the pilot-study; the evaluation of the larger groups of children with cerebral palsy is being planned. In the authors ‘opinion the objective method of CP children gait evaluation may be the helpful tool for clinicians to optimize the way of CP children treatment.