Cerebral edema and increased ICP in post OHCA patients can be harmful due to the brain’s rigid encasement, although the increase is small. Lumbar CSF drainage (LD) may be a valuable treatment for refractory increased ICP in patients with discernible basal cisterns. Furthermore, much of the CSF volume is located in the subarachnoid spaces, which are not accessible for drainage by ventriculostomies. However, there has been no study on the effect of LD in OHCA patients. Therefore, we investigaed whether LD reduces mortality and improves neurological prognosis in OHCA patients who underwent TTM. This was a prospective single-center study conducted from July 2021 to April 2020 (CNUH IRB201907033003, NCT04328974). The target temperature of 33°C was maintained for 24 h, and LD was initiated when ICP exceeded 15 mmHg at the rate of 10 ml per hour via a LD catheter until ICP was less than 15 mmHg. We performed propensity score matching with the CAHP score variables between the group with and without LD. We used the binary logistic regression and the Cox proportional hazard regression with the NULL PLEASE score variables. After propensity score matching, 50 patients were selected in each group (Fig.1, Table 1). Serum levels of NSE and the percentage of brain tissue with ADC value < 650 X 10 -6 mm 2 /s (PV 650 ) obtained 72 h after ROSC were lower in the group with LD (Table 2). The analysis revealed that LD was associated with good neurological prognosis and increased the probability of survival (Table 3, Fig. 2). The subgroup analysis, focusing on OHCA patients with moderate severity based on the rCAST score, yieded consistent results (Table 4, Fig. 2).This study demonstrated that LD significantly improved neurological prognosis and reduced mortality in OHCA patients with moderate severity.