PURPOSE: Suicide attempts are known to be influenced by mass media reports. The purpose of this study was to evaluate the effects of mass media reporting celebrity suicides on an increase of intentional carbon monoxide (CO) poisoning and suicide attempts. METHODS: We retrospectively reviewed the medical records of the consecutive patients who presented with suicide attempts to the Emergency Department of Ajou University Hospital during a 24 month period. We obtained the demographic data, any past history of suicide attempt and the methods of suicide attempts from the medical records of the suicide attempters. Time series analysis was conducted for evaluating the influence of mass media reporting of celebrity suicide on the suicide rates. RESULTS: We finally enrolled 770 patients during the study period. The total number of suicide attempts by CO poisoning was 18 and the average number of suicide attempts by CO was 0.33+/-0.73 per week. All of the suicide attempts by CO poisoning occurred after a celebrity committed suicide using CO from burning charcoal. CONCLUSION: This study showed that celebrity suicide by CO poisoning resulted in the Werther effect, which made the rate of intended CO poisoning increase, and the study provided further evidence for the need to actively restrain mass media reporting of suicide to decrease the Werther effect.