- Background Pneumonia is diagnosed by a combination of clinical symptoms and findings on chest X-ray (CXR). However, there is often disagreement, even among experts, upon the interpretation of the CXR. The purpose of this study was to compare the agreement rates in CXR interpretation of suspected community-acquired pneumonia (CAP) between a radiologist, a pulmonologist, an infectious disease specialist, and an internal medicine staff and to establish the correlation of such an agreement with the length of hospitalization and 30-day mortality rate. Methods We prospectively enrolled in our study all patients admitted to the Department of Medicine with suspected CAP, as defined by the admitting physician, within the first 24 h of hospitalization. A radiologist, pulmonologist, and infectious disease specialist who were aware of the suspected diagnosis independently interpreted the CXR. The final diagnosis was obtained from the discharge notes. Results A total of 262 patients participated in the study, 214 of whom (81.7%) were eventually discharged with a diagnosis of CAP. The agreement rates between the readers of the CXR ranged from a kappa of 0.09 to 0.44. There were no differences in terms of background illness, PORT (Pneumonia Patients Outcomes Research Team) score, length of hospitalization, or mortality rates between patients discharged with or without a diagnosis of CAP. In multivariate analysis, only the PORT score was a significant predictor of length of hospitalization and mortality rate. Conclusion We found a low to moderate agreement rate of the diagnosis of CAP between CXR readers. Identification of an infiltrate on CXR, either by specialists or by the attending physician, did not impact the clinical outcomes.