Objective : There are few studies comparing small and large craniotomies for the initial treatment of chronic subdural hematoma (CSDH) which had non-liquefied hematoma, multilayer intrahematomal loculations, or organization/calcification on computed tomography and magnetic resonance imaging. These procedures were compared to determine which would produce superior postoperative results. Methods : Between 2001 and 2009, 317 consecutive patients were surgically treated for CSDH at our institution. Of these, 16 patients underwent a small craniotomy with partial membranectomy and 42 patients underwent a large craniotomy with extended membranectomy as the initial treatment. A retrospective review was performed to compare the postoperative outcomes of these two techniques, focusing on improvement of neurological status, complications, reoperation rate, and days of post-operative hospitalization. Results : The mean ages were $69.4{pm}12.1$ and $55.6{pm}9.3$ years in the small and large craniotomy groups, respectively. The recurrence of hematomas requiring reoperation occurred in 50% and 10% of the small and large craniotomy patients, respectively (p<0.001). There were no significant differences in postoperative neurological status, complications, or days of hospital stay between these two groups. Conclusion : Among the cases of CSDH initially requiring craniotomy, the large craniotomy with extended membranectomy technique reduced the reoperation rate, compared to that of the small craniotomy with partial membranectomy technique.