PURPOSE: To evaluate, using magnetic resonance (MR) imaging, the clinal significance of the corpus callosum by measuring the size of various portions of the corpus callosum in children with cerebral palsy, and in paired controls. MATERIALS AND METHODS: Fifty-two children [30 boys and 22 girls aged between six and 96 (median, 19) months in whom cerebal palsy was clinically diagnosed underwent MR imaging. There were 23 term patients and 29 preterm, and the control group was selected by age and sex matching. Clinal subtypes of cerebal palsy were classified as hemiplegia(n =14), spastic diplegia(n=22), or spastic quadriplegia(n=16), and according to the severity of motor palsy, the condition was also classified as mild(n=26), moderate(n=13), or severe(n=13). In addition to the length and height of the corpus callosum, the thickness of its genu, body, transitional zone and splenium, as seen on midsagittal T1-weighted MR images, were also measured. Differences in the measured values of the two groups were statistically analysed and differences in the size of the corpus callosum according to the clinical severity and subtypes of cerebral palsy, and gestational age, were also assessed. RESULTS: Except for height, the measured values of the corpus callosum in patients with cerebral palsy were significantly less than those of the control group (p < 0.05). Its size decreased according to the severity of motor palsy. Compared with term patients, the corpus callosum in preterm patients was considerably smaller (p< 0.05). CONCLUSION: There was statistically significant correlation between the severity of motor palsy and the size of the corpus callosum. Quantitative evaluation of the corpus callosum might be a good indicator of neurologic prognosis, and a sensitive marker for assessing the extent of brain injury.