Purpose: This study reports the clinical features of infant, child, school aged and adolescent patients treated for acute poisoning in nationwide emergency departments (EDs). Methods: We retrospectively analyzed clinical data pertaining to patients under 19 years of age who were treated for acute poisoning in nationwide EDs from 2013 to 2015. The data were collected by the National Emergency Department Information System (NEDIS). All patients were divided into three groups: 'Infant and child group' (0 to 5 years), 'school age group' (6 to 12 years) and 'adolescent group' (13 to 18 years). General characteristics, Korea Standard Classification of Disease $7^{th}$ (KCD-7) codes and results of care were collected. Results: There were 14,500 pediatric poisoning cases during the study period. The distribution of patient age was bimodal with two peaks among infant, child and adolescent group. The proportion of alert mentality at the ED visit of the infant and child group was 99.3%, while that of the adolescent group was 86.4%. The proportion of intentional intoxication was higher in the adolescent group (40.7%) than other age groups. Among children less than 13 years of age, various poisonous substances and therapeutic drugs were common. Conclusion: There were some clinical differences in acute poisoning patients between age groups. It is necessary to establish a preventive plan considering characteristics by age. Since the KCD-7 code has limitations in analyzing the characteristics of poisoning patients, it is necessary to consider the registration system of poisoning patients.