BACKGROUND: Therapeutic hypothermia (TH) has recently been recommended and widely used in post-resuscitated patients after cardiac arrest. In Korea, however, the use and study of this method are rare. We investigated outcomes and factors associated with survival in elderly patients who received TH after out-of-hospital cardiac arrest (OHCA). METHODS: We reviewed the cases of 38 elderly (> or =60 years) and 50 younger (<60 years) patients who received TH after OHCA from January 2007 to December 2008. We compared the outcomes and factors associated with mortality in the pre-, intra- and post- cardiac arrest periods of both groups. RESULTS: The elderly (> or =60 years) had higher mortality (22 [57.9%] vs 15 [30.0%], p=0.023) and poorer neurological outcome (34 [89.4%] vs 36 [60.0%], p=0.002) than the younger patients (<60 years). Factors associated with survival in the elderly were arrest at home (31.3% vs 63.2%, p=0.049), pH (7.16+/-0.18 vs 7.00+/-0.13, p=0.008), base deficits (-11.26 +/- 4.74 vs -15.33 +/- 5.50 mmol/L, p=0.029) and lactate level (7.75 +/- 2.87 vs 10.7 +/- 3.58 mmol/L, p=0.013) while pH (7.13 +/- 0.16 vs 6.99 +/- 0.14, p=0.028) and APACHE II scores (19.46 +/- 5.70 vs 24.13 +/- 4.44, p=0.005) affected survival in the younger patients. However, there was no significant difference in complications related to TH. In logistic regression analysis, factors related to mortality at 1 month were age, time from collapse to Advanced Cardiac Life Support, arterial pH and presence of seizure. CONCLUSION: The elderly have worse neurological outcome and survival rate post resuscitation. Factors associated with survival were mainly related to low flow during cardiac arrest. However, there was no significant influence from complications during TH on survival. Thus, TH can be administered safely to elderly patients for successful resuscitation after cardiac arrest. Further study on the effects of TH in the elderly should be done.