Hydranencephaly is congenital disorder involving total or near-total absence of cerebrum, but with intactmeninges and cranial vault. CT offered a unique diagnostic tool for the evaluation of these infants, but diagnosisas well as precise localizatio of anomaly can be provided. We analysed US and CT findins of 5 patients, wtihhydranencephaly who examined at Sung Ae General Hospital during last 3 years. The results were as follows: 1. 3 patients were diagnosed wtih aged in 11 days to 40 days. 2 patients were diagnosed in prenatal US examination with intrauterine pregnancy 40 weeks and 28 weeks. The male to female ratio was 3:1(unknown sex in one case with intrauterine pregnancy 28 weeks). 2. Cranial vault and brain stem were intact in 5 cases. 3. Cerebellum was absentin 1 case and intact in 4 cases. 4. Falx cerebri was intact in 2 cases, partial defect in 1 case and absent in 2cases. 5. Remnant cerebral hemisphere were as follows; partial and unilateral parietal lobe in 3 cases, both parietal lobes in 1 case, parietal and unilateral occipital lobes in 1 case, thalamus and basal ganglia in 1 case. 6. All cavities were seen in echofree cystic nature in US and low densities in CT. 7. 4th ventricle was seen in 4cases, 3rd ventricle in 2 cases and lateral ventricles communicating with echofree cystic areas. 8. Polyhydramniosand macrocephaly were seen in 2 cases in prenatal US examination.