The evaluation of pleuritic pain in the emergency department (ED) presents a considerable challenge for the attending physician. Chest radiography (CXR) is a basic test, but its sensitivity is low, and often more sophisticated imaging techniques are needed. Our aim is to assess the diagnostic value of bedside B-mode lung ultrasound (LUS) in the visualization of radio-occult pulmonary lesions. Forty-nine patients complaining of pleuritic pain with negative CXR were prospectively studied by LUS. Detection of at least one of the following sonographic signs in the painful thoracic area was considered diagnostic: (i) the absence of pleural sliding; (ii) the focal alveolar-interstitial syndrome (AIS), defined by multiple artifacts B-line; (iii) the peripheral alveolar consolidation (PAC), defined by hypoechoic subpleural images; and (iv) the pleural disruption with thickening and irregularity of the line, with or without localized effusion. The final diagnoses were confirmed by spiral CT scanning (n = 12) and follow-up (n = 37). Final diagnoses were chest wall pain (n = 30), pleuropneumonia (n = 14), pulmonary embolism (n = 4), lung metastasis (n = 1). In 18 patients of the group with pulmonary conditions, LUS showed signs of pleurisy. They were PAC (n = 12), AIS (n = 17), pleural disruption (n = 17). If any sign is considered, the sensitivity of LUS in the diagnosis of radio-occult lesions was 94.7%, specificity was 96.7%, positive and negative predictive values were 94.7% and 96.7%, respectively, and accuracy was 95.9%. In patients with pleuritic pain of unknown cause, real-time LUS enables the diagnosis of radio-occult lung and pleural lesions.