Consequences of neuromuscular impairment may lead to lung damage and reduced lung function in children with cerebral palsy (CP). The purpose of this study was to evaluate chest mobility by means of chest expansion (CE) measurements in patients with spastic CP. Chest circumference at maximal voluntary inspiration (Cinsp) and at maximal voluntary expiration (Cexpir) and CE (the difference between Cinsp and Cexpir) were measured in 56 consecutive inpatients with spastic CP and in 40 healthy children. CE was significantly decreased (p < 0.001) and Cexpir was increased (p < 0.02) in the CP group, while mean Cinsp values were not statistically different (p > 0.05). The difference between CP patients and controls with respect to CE was becoming more prominent in older children. As chest mobility is decreased in spastic CP patients, early initiation of pulmonary rehabilitation, which may improve and maintain chest mobility and respiratory function, seems reasonable in this patient group.