Maintenance of stability for children in a wheelchair, particularly for those with spasticity, can be achieved through external stabilization components, such as pelvic positioning belts. Different kinds of pelvic belts exist on the market and one of the main characteristics is the different number of attachment points between the seat and the belt. As literature on this topic is limited to qualitative assessments, this study compared quantitatively 4-point versus 2-point pelvic positioning belts for the trunk fixation in 20 young patients with spasticity. Our data showed that 70% of the children required the use of pelvic belts on wheelchairs for stability and a better stability was observed with the 4-point belts than compared to the 2-point. Data generally showed in fact a higher percent of variation in terms of trunk flexion angleand knee joint angle with the 2-point belt than the 4-point belt, indicating increased submarining with the 2-point belt during sitting maintenance if compared to the 4-point belt (p < 0.05). According to our results, the 4-point belts seem to be the most effective configuration for patient stabilization, suggesting that its use prevents the thigh from submarining.