Subdural hygromas occur after various brain interventions, are often asymptomatic but sometimes may require surgical treatment. They can develop in the immediate postoperative period, but they are more common a few weeks or even months after surgery. Subdural hygromas are particularly common after decompressive craniotomy in patients with traumatic brain injury or massive stroke. The pathogenesis is explained by the fact that a large bone defect causes a pressure difference in the skull, and a concomitant displacement of the ventricular system disrupts the normal cerebrospinal fluid circulation, contributing to the redistribution of cerebrospinal fluid flow into the subdural space.We review data from contemporary studies on subdural hygromas after decompressive craniotomy, their risk factors, and management strategies. We also present our case of recurrent subdural hygroma in a patient operated on for a ruptured aneurysm of the middle cerebral artery.