Objectives: To evaluate the relationship between clinical features evaluated at admission to the emergency department (ED) and the presence of infection on thoracic and abdominal tomography (CT) scans in patients with acute febrile illness without clinical clues. Methods: Patients aged 18 years and over who presented to ED with acute fever between January 1, 2020 and December 31, 2020 and underwent CT imaging (thoracic and abdomen) as a diagnostic test CT) were included in the study retrospectively. The patients were divided into two groups according to the presence and absence of a source of infection on CT. The clinical and demographic data of the patients were evaluated. The effect of clinical factors on the presence of infection in CT scans was determined using the logistic regression analysis. Results: Among the 173 patients included in the study, the CT scans were positive for the source of infection in 31.2% (n=54) and negative in 68.8% (n=119). In the multiple logistic regression analysis, age ≥ 65 years [odds ratio (OR):2.72, 95% confidence interval (CI):1.15-4.35, p<0.001), presence of comorbidity (OR:2.37, 95% CI:1.08-4.14, p=0.033), and procalcitonin positivity (PCT) (OR:2.54, 95% CI:1.29-4.95, p=0.006) were identified as risk factors for the presence of infection in CT. Conclusion: Age, presence of comorbidity, and PCT level should be considered when deciding on the use of CT in determining the source of infection in acute febrile patients without clinical clues.