The primary objective was to evaluate the characteristics of adults (≥18 years old) with chronic pediatric disorders (transition patients) who visited the pediatric emergency department (PED). The secondary objective was to determine the associated factors for their admission.This study was a retrospective chart review of transition patients seen at a large, urban PED in Korea from 2010 to 2015. Epidemiologic and clinical data were used to identify the characteristics of transition patients compared with those of pediatric patients in the PED. A multivariable logistic regression model was used to calculate odds ratios (ORs) for the factors associated with hospitalization.Transition patients accounted for 2776 (2.4%) of the total encounters. A total of 463 (38.9%) of the transition patients had >1 visit. Congenital heart disease was the most common (23.2%) chronic pediatric disorder. Most encounters (94.5%) were related to an underlying disorder, and 34.4% of the encounters required consultations with other pediatric subspecialties. Diagnostic procedures were performed in 90.1% of the encounters. Transition patients were hospitalized more than pediatric patients (35.3% vs 15.3%; P < .001). The associated factors for admission in the transition patients were chronic gastrointestinal disorder (adjusted odds ratio [AOR]: 3.76 [95% confidence interval, CI, 2.29–6.16]), complaints related to an underlying disorder (AOR: 3.13 [95% CI, 1.94–5.05]), respiratory complaints (AOR: 2.02 [95% CI, 1.33–3.08]), and infectious complaints (AOR: 1.97 [95% CI, 1.40–2.76]).A substantial number of transition patients used the PED, and they required a larger amount of resources in the PED. Chronic gastrointestinal disorder, respiratory symptoms, or complaints related to an underlying disorder were the related factors for admission of transition patients.