The decompressive craniectomy (DC), procedure that may be necessary to save lives of patients suffering from intracranial hypertension, is not complication-free. The two main complications are hydrocephalus and the sinking skin flap syndrome (SSFS). The radiological findings and the clinical evaluation may be not enough to decide when and/or how to treat hydrocephalus in a decompressed patient. SSFS and hydrocephalus may be not unrelated. In fact, a patient affected by hydrocephalus, after the ventriculoperitoneal shunt, can develop SSFS; on the other hand, SSFS per se can cause hydrocephalus.Treating hydrocephalus in decompressed patients can be challenging. Radiological findings and clinical evaluation may not be enough to define the most appropriate therapeutic strategy. CSF dynamics and metabolic evaluations can represent important diagnostic tools for assessing the need of a CSF shunt in patients with a poor baseline neurologic status. Based on our experience, we propose a flow-chart for treating decompressed patients affected by ventriculomegaly.