Purpose: The purpose of this study was to evaluate the effects of BLS training in nursing students and their retention period. Methods: The participants were 48 nursing students enrolled in M University in Mokpo. Data were collected from September, 2009 through September 2010. Nursing students were tested for their knowledge, attitude, confidence before, immediately after, 4 weeks after, 8 weeks after, 6 months after, and 1 year after BLS training. In addition, their knowledge and skill of cardiopulmonary resuscitation were tested 5 times. Data were analyzed using the SPSS/PC 12.0 statistical program Results: Knowledge, attitude and confidence were significantly increased immediately after compared to before BLS training. Knowledge and confidence 6 months after, and attitude, performance ability and technical precision for ventilation and compression 4 weeks after BLS training were significantly decreased compared to immediately after. Conclusion: Overall retention of BLS training effects among nursing students, without reinforcement, decreases significantly after six months following initial training. BLS training in nursing students should be repeated every six months, especially performance training of BLS should be repeated every 4 weeks. In addition, to maintain the knowledge and skills of BLS, appropriate renewal time of certification and improvement of training programs are necessary.