Background: Traumatic subdural hydroma (TSH) is a common complication of head injuries. The aim of this study was to examine the clinical characteristics and classification of TSH. Methods: One hundred and ninety-two patients with TSH were treated in Qilu hospital during a 13-year period (1989–2001). We reviewed each patient’s clinical records and radiological findings. Results: Based on clinical features and dynamic observation of CT scanning, TSHs were classified into four types: resolution, steadiness, development and evolution. The resolution type often occurred in the prime of life, and the patients had normal intracranial pressure and good prognoses after conservative treatment. The elderly made up the majority of the steadiness type. Their main clinical manifestations included headaches, dizziness, nausea, vomiting, abnormalmentality, etc. Generally, no positive nervous systemic sign related to TSH was observed. The prognoses of the steadiness type treated by conservative therapy were also satisfactory. The development type was common in babies and children and mainly manifested as progressively increasing intracranial pressure, mild hemiplegia, aphasia and abnormal mentality. The patients with development type often needed surgical treatment where there was an associated risk of dying from accompanying cerebral parenchymal damage or postoperative complications once in a while. The evolution type with chronic subdural haematoma occurred between 22 and 100 days after TSH and in the cases of small hydromas treated conservatively, with mild accompanying cerebral damage, characterised by the polarised age, and chronic increased intracranial pressure, there was always a good prognosis after surgery. Conclusions: The mechanism, clinical characteristics, treatment methods and prognoses varied with the different types of TSH.