OBJECTIVE: Understanding warning signs for suicide is a crucial aspect of suicide prevention. This study was designed to compare warning signs prior to suicide attempt by self-immolation versus suicide attempt by self-poisoning among consecutive referrals for treatment after suicide-attempt at Kermanshah Imam Khomeini Hospital, Iran. METHODS: Over a 4-month period (June-September 2008), first degree relatives of 200 consecutive patients referred to Kermanshah Imam Khomeini Hospital, Iran, following a suicide attempt were interviewed. Sixty-three patients had attempted suicide by self-immolation and 137 by self-poisoning. Interviews addressed demographic characteristics (gender, age, marital status, and educational status) and three sets of psychosocial warning signs for suicide (verbal, behavioral, and environmental). RESULTS: Four significant differences in types of warning signs were found between the two groups. Those patients who had attempted suicide by self-poisoning were more likely to have shown seeking behavior for killing devices prior to the suicide (p<0.001), to have shown depressed mood and severe changes in mood (p<0.01), to have shown a lack of interest in work and education (p<0.02), and to have shown reckless behaviors (p<0.01). Other symptoms were not significantly different between the groups. Analyses considering warning signs in clusters of behavior patterns (verbal, behavioral, and environmental warning signs) indicated behavioral warning signs were more common in patients who had attempted suicide by self-poisoning. Further, the total number of warning behaviors was greater in the self-poisoning group (p<0.001), indicating that the group who attempted suicide by self-poisoning seemed to do so with more substantial planning and warning than those who attempted suicide by self-immolation. CONCLUSION: Warning signs for suicide by self-immolation were different and fewer than warning signs for suicide by self-poisoning among this sample of 200 Iranian patients who had attempted suicide. Prediction and prevention of suicide by self-immolation may be more difficult than prevention of suicide by other methods.