Purpose: To compare the Appropriateness of abdominal CT to abdominal radiography as an imaging modality in terms of the diagnostic value, medical costs and decision making times for patients presented to the emergency department with nontraumatic abdominal pain. Methods: This study used the records of 530 cases presented to the emergency department(ED) with nontraumatic abdominal pain from February to March 2012. Imaging modalities were categorized into abdominal radiography and CT (radiography first or CT first) or radiography alone or CT alone. The diagnostic value, total medical costs and effect on decision making time of the each imaging modalities were compared. Especially, in retrospective review, to evaluate the predictability of the abdominal radiography, alit was assumed that all the 530 cases performed that exam as initial imaging. Results: Among 530 cases, 255 cases underwent abdominal radiography only, 28 cases underwent abdominal CT only and the remnant 247 cases underwent abdominal CT with plain abdominal radiography. The diagnostic value was higher in the cases with abdominal CT (268/275, 97.5%) than in the cases with plain abdominal radiography (19/255, 7.5%).The number of cases predicted by abdominal radiography only as initial imaging were 39/530 (7.4%). In cases where the patients performed the abdominal CT as the first imaging modality thereby omitting the abdominal radiography, the total diagnostic imaging fee was lower than in cases with plain abdominal radiography first followed by the abdominal CT (277,140 vs. 284,226(mean, Korean Won)). Although diagnostic value of the plain abdominal radiography as first imaging modality was lower than the abdominal CT, Decision making time, average duration of hospital stay was longer and the total medical costs was higher than abdominal CT. Conclusion: As an imaging modality in the ED for patients with acute nontraumatic abdominal pain, plain abdominal radiography is an avoidable procedure when viewed in terms of the diagnostic value and total medical costs and decision making times comparing with abdominal CT.