Pathological reactions to traumatic events have been reported in the literature for more than one hundred years. Parental loss as a traumatic event leads to a measurable degree of symptomatic disorder. The present study aims to determine the role of personality characteristics of children and adolescents who have lost their parents in the occurrence of PTSO symptoms in these subjects, and to specify which demographic variables, types of parental loss, type of personality and other relevant variables are predictor factors for PTSO. One hundred and forty four children and adolescents who had lost their parents were studied. From the total sample, 39 were survivors whose parent(s) died through the 1990 earthquake in Iran and were considered as a study group. One hundred and five children, who had lost their parents through natural death, divorce or, separation in Tehran, were considered as a comparison group. Three research instruments (CPTSO-RI, CAPS, and JEPQ) were used in this study. The results of the study showed that 48.7% of the study group and 20% of the comparison group met the criteria for PTSO symptoms. Subjects who had lost their parents through death were more at risk than children and adolescents whose parents were divorced or separated. In this particular study, girls reported a higher level of PTSO symptoms than boys. Multiple exposure to the traumatic events was found to be a factor of importance in predicting PTSO. Subjects with higher scores on Neuroticism and Psychoticism were more likely to show PTSO symptoms, whereas children and adolescents with higher scores on the Extroversion were less likely to meet the criteria for PTSD symptoms.