Deformational plagiocephaly, cranial asymmetry secondary to positioning, continues to be a leading cause of head shape abnormalities in infants. Treatment recommendations include nonintervention, positioning therapies, and helmet therapy. Although most agree that surgical intervention is rarely indicated, the ideal therapy is not agreed on. Some even debate the necessity of treatment, especially third-party payers. The purpose of this prospective study is to use an objective outcome analysis tool, computerized tomography, to assess the efficacy of a soft shell helmet therapy. Sixty-nine children with a diagnosis of deformational plagiocephaly were enrolled in this study to assess the success of a soft shell helmet for the correction of cranial asymmetry. Computed tomography scanning was done before therapy and 6 months after the initiation of therapy. Three-dimensional reconstructions of these scans were reformatted into a standardized orientation by utilizing the nasion (radix), frontozygomatic suture lines, and posterior aspect of the foramen magnum. Intracranial volumes were calculated on a quadrant basis, and asymmetry was evaluated with regard to the hemispheres (left versus right) and the posterior quadrants. Thirty-four children (27 boys and 7 girls) completed the study protocol. The side involved was the right in 62% of cases and the left in 38%. Mean age at the initial scan was 6.3 months, and mean age at the follow-up scan was 14 months. Mean duration of helmet therapy was 7 months. Compliance with therapy was average to above average in 88% of the children and poor in 12%. There was a 36% to 54% improvement in asymmetry in the compliant patients over the 6-month study period. Soft shell helmet therapy is an effective technique to decrease cranial asymmetry based on objective outcome measurements. Additionally, it is cost-effective, with the total cost of therapy for the helmet and office visits ranging from $600 to $700. This therapy compares favorably with other more expensive and time-consuming therapies that have been reported in the literature.