ABSTRACT Received: 16 August 2014 Accepted: 13 December 2014 Key words: Arachnoid cyst, Chronic subdural hematoma, Posttraumatic intracranial hypertension Background: Chronic subdural hematomas (CSDH) tend to occur in elderly patients with a history of mild head injury few weeks prior to the onset of symptoms. Arachnoid cysts (AC) are relatively common congenital intracranial mass lesions that arise during the development of the meninges. However, these two distinct clinical entities sporadically occur together in relatively young patients. Objective: In light of a literature review, a trial to explain the association between arachnoid cyst and subdural hematoma is proposed. Patients & Methods: This is a report of four cases presented with chronic subdural hematoma over the frontoparietal region, with an incidental finding of an arachnoid cyst over the Sylvian fissure. Results: Three patients were males and one female. Age ranged from ten years to forty one years. All patients had history of minor head trauma. Their symptoms were due to intracranial hypertension, like those with isolated CSDH. All patients’ symptoms regressed after evacuation of CSDH. Conclusion: Arachnoid cyst is a possible risk factor for subdural hematoma in young adults. A burr hole procedure with drainage of hematoma is an adequate treatment. © 2014 Egyptian Journal of Neurosurgery. Published by MEDC. All rights reserved