Objective The aim of this study was to investigate the accuracy of bedside lung ultrasound (BUS) in the diagnosis of community-acquired pneumonia (CAP) in patients with dyspnoea presenting to the emergency department (ED) and to analyse the characteristic sonographic findings of CAP. Methods After a six-hour training program, BUS procedures were performed between October 2011 and February 2012 to prospectively evaluate patients presenting to the ED with dyspnoea. Chest X-ray (CXR) or computerised tomography (CT) were ordered, depending on the presence of consolidation signs on CXR. The outcome was determined by consolidation findings on CXR or CT. BUS results were compared using Chi-squared testing. Results Of the 112 enrolled patients with dyspnoea, 40 patients were excluded and 72 were included in the study. Thirty-four patients were BUS positive. Of these, CXR or CT findings agreed with the BUS findings in 27 patients. In 38 cases, BUS was negative, and one patient was diagnosed with pneumonia based on the CT report. The sensitivity, specificity, PPV, NPV, and the positive and negative likelihood ratios for BUS were 96.4%, 84.1%, 79.4%, 97.4%, 6.1 and 0.042, respectively. The diagnostic accuracy of BUS was 89%. The presence of consolidation signs, either shred or hepatisation, were the most frequent sonographic findings in our study. Conclusions Acute alveolar consolidation can be diagnosed easily by performing BUS with high degree of accuracy in EDs.