Subdural hematomas (SDH) ar relatively common and the typical CT findings according to the age of them arewell established. The results were as follows: 1. The most common cause of SDHs was the direct trauma which wasnoted in 60 cases(73.2%). 2. The atypical CT findings of the mixed density were seen in 19 cases(23.2%), includingacute SDH 7 cases (20%), subacute SDH 5 cases (41.7%), and chronic SDH cases(20%). 3. The possible causes of themixed density in acute SDH were unclotted blood in early stage of hematoma development or serum extruded duringthe early phase of clot retraction. But the possibility of cerebrospinal fluid within subdural space due to anarachnoid tear could not be excluded. 4.The possible causes of the mixed density in subacute and chronic SDH wereserum extruded during the hematoma resuolution and rebleeding. 5. Wall enhancement of hematomas was noted in 3cases(25%) of subacute SDHs and 15 cases(42.9%) of chronic SDHs. 6. Most of SDHs was crescentic in shape, butlenticular in 4 cases(4.9%). Midline shift and compression of ventricles were proportional to the maximumthickness of SDHs. There were seen ipsilateral dilatation of ventricles in 9 cases(11.0%) and brain edema in 11cases(13.4%).