To investigate the patients who underwent decompressive craniectomy (DC) for trauma or cerebrovascular disease, and to determine the most suitable treatment protocol for those patients. Overall, 32 patients with trauma or cerebrovascular disease underwent DC. Clinical, radiological and surgical data of surviving patients was retrospectively analysed. The occurence of favourable and unfavourable outcomes during the course of their treatment were recorded. We detected ventriculomegaly in nine out of the 32 patients (9/32, 28.1%) after DC. Of these nine, four patients (4/9, 44.4%) underwent shunt surgery. Cranioplasty performed in 29 of the 32 patients caused epidural hygroma in 13 of them (13/29, 44.8%). Of these 13 patients, three underwent surgery because of progressive increase in the size of hygromas. In the remaining patients, the epidural hygromas regressed spontaneously. Glasgow coma score (GCS) before and after DC surgery (p=0.011 and p=0.006, respectively), timing of cranioplasty (p=0.028), midline shift (p=0.048) and craniectomy size (p=0.047) were significantly associated with ventriculomegaly. Lower GCS, delayed cranioplasty, greater midline shift and larger craniectomy size were found to be associated with hydrocephalus after DC. To avoid hydrocephalus, it may be beneficial to perform shunt surgery first followed by cranioplasty in a single surgical procedure. Additionally, epidural hygromas frequently encountered after a cranioplasty that should be considered and followed up carefully.