Croup is the leading infectious disease resulting in pediatric upper airway obstruction. Our purpose is to analyze diverse features of neck radiographs could be seen as an objective tool to predict outcomes in patients with croup. One hundred and ninety-two patients were prospectively recruited in pediatric emergency department with diagnosis of croup. The initial Westley score (WS), presence of steeple sign, extent of narrowing, and narrowing ratio on soft tissue neck radiographs were determined before and after treatments. The extent of frontal narrowing, extent of lateral narrowing, frontal ratio (FR), and lateral ratio (LR) were investigated to predict clinical outcomes in patients with croup. The extent of frontal/lateral narrowing and LR had significant correlation with outpatient status. Almost 71% of patients with FR values below 0.23 stayed in the hospital longer, whereas nearly 98% of patients with FR vales above 0.65 could be discharged. About 85% of patients with LR below 0.45 hospitalized longer. The LR and FR were significantly correlated with the severity and admission rate in croup. The LR > 0.6 and FR > 0.65 may indicate low risk in patients with croup, whereas the FR < 0.23 or LR < 0.45 may indicate the need of stay in hospital for further treatment and monitor.