To determine, in an Emergency Department (ED) population, the incidence of pneumonia diagnosed on thoracic computed tomography (CT) in the setting of negative or non-diagnostic chest radiographs (CXR). This is a retrospective chart review of all ED visits of adult patients ultimately diagnosed with "pneumonia" in whom both CXR and CT were obtained. We note cases in which the CXR was either negative or non-diagnostic for pneumonia and the CT noted a definitive infiltrate consistent with pneumonia. Of the 1,057 patients diagnosed with pneumonia, both CXR and CT were performed in 97 cases. Of this group, there were 26 patients (27%), in whom the CXR was either negative or non-diagnostic, but the CT noted an infiltrate/consolidation consistent with pneumonia. In our retrospective review of ED patients, we find that in 27% of cases in which both a CXR and a CT scan were performed in the work-up of varied chief complaints, pneumonia was demonstrated on CT in the face of a negative or non-diagnostic CXR. This analysis demonstrates the need for further studies regarding the appropriate radiographic evaluation of pneumonia, particularly in high-risk patients.