We describe three children born at term investigated for neonatal seizures or transient apnoea. Cranial ultrasound and MRI unexpectedly revealed symmetrical periventricular cysts adjacent to the anterior horns. We found no evidence of prenatal viral infection, intraventricular or subependymal haemorrhage or hypoxic-ischaemic lesions. The lesions were not seen on MRI at 3 months of age, but there was no compensatory dilatation of the anterior horns nor secondary loss of white matter. The appearance and location of these transient cysts were different from those of the cystic changes which typically follow germinal matrix haemorrhage or periventricular leukomalacia. Their pathogenesis and clinical significance remain to be determined.