CT brain scans were used to evaluate the most likely etiology of hemiplegic cerebral palsy in a group of children born at term. The population based study group comprised 83 children. The CT findings were classified to reflect the phase of brain maturation during which the injury causing hemiplegia most likely had occurred. The most common finding (37\%) was periventricular atrophy considered to represent periventricular leukomalacia (PVL). PVL is a form of hypoxic-ischemic damage typical of the immature brain and most commonly seen as a complication of preterm birth. As this lesion was found in children born at term it was considered to reflect a cerebral injury that had occurred in utero. Cerebral maldevelopment, due to a very early intrauterine lesion, was detected in 17\%, while cortical-/subcortical lesions, previously considered to be of major importance in hemiplegia, were seen in just 16\% of the children. Altogether the CT findings indicated a prenatal origin of hemiplegia in 57\%. Assessing the time of injury based on clinical records concurred with prenatal origin in 32\% of the children thought to have prenatal origin of hemiplegia by CT. The objective information available from careful review of imaging information such as CT brain scans, is an important adjunct to clinical data. We propose that assessment of brain morphology, by means of imaging, should be integrated with clinical assessment when evaluating the etiology of brain lesions in children with congenital motor impairment.