OBJECTIVE The purpose of this study was to report the clinical and imaging findings of seven children who developed extraaxial, intracranial hemorrhage 3-12 years after suboccipital craniectomy for neoplasia. We attempt to explain the hemorrhages based on a previously reported hypothesis of neomembrane formation associated with dural substitutes used to repair large dural defects. METHODS Clinical charts (seven patients), surgical and pathologic findings (four patients), and imaging studies (CT scans and MR images in four; CT scans, MR images, and angiograms in one; and CT scans only in two patients) were reviewed retrospectively. Hemorrhage occurred 3-12 years after suboccipital craniectomy for tumor (ependymoma in two, medulloblastoma in three, astrocytoma in one, and ganglioglioma in one). Silastic dural substitute was used to repair the surgical wound in six cases and human dural graft in one case. Hematomas were spontaneous in four and occurred after minor head trauma in three. Four patients had multiple hemorrhagic episodes. RESULTS CT scans and MR images showed acute extraaxial hemorrhages at the craniectomy site without contiguous residual or recurrent neoplasia in all patients. No intraaxial or intratumoral hemorrhage was detected. Findings on cerebral angiograms in one patient were normal. Four patients underwent surgical exploration of the hematoma and craniectomy site; no macroscopic source of bleeding was detected. The hematomas were not associated with recurrent tumor pathologically. CONCLUSIONS Delayed, benign extraaxial hematomas may occur in children who have undergone craniectomy for tumors of the posterior fossa and have had dural substitute used to repair large defects. Fragile vessels associated with nonmembranes have been proposed as the source of hemorrhage.