Background: Different imaging techniques can be used for assessment of chest problems in ICU patients, however ultrasound is a good diagnostic tool giving more information and at the same time without exposure to radiation and without risk of critical patient transfer. Aim of work: To compare the diagnostic performance of transthoracic ultrasound (TUS) and bedside chest radiography (CXR) for the detection of various pathological abnormalities in critically ill patients, using computed tomography (CT) as a gold standard. Sixty four patients was admitted in RCU . CXR , CT and TSU was done to all patients . six pathological entities were evaluated: pleural effusion, pneumothorax, consolidation and interstitial syndrome ,pulmonary embolism and neoplasm . Results: All patients were evaluated by the three imaging techniques. The sensitivity, specificity of CXR were was 42.1% , 84.4% for pneumonia 50.0%,90.0% for pleural effusion. 45.5% ,90.6% for Interstitial syndrome . 50.0% ,94.8% for pneumothorax 60%,100% For pulmonary embolism .66% ,94% for neoplasm .while the corresponding values for Chest US were 89.47% ,100% for pneumonia . 60%, 100% for pulmonary embolism . 100%, 100% for pleural effusion , pneumothorax , Interstitial syndrome and neoplasm . Conclusion: Ultrasound examination of the chest is a non- invasive, and promising bed side tool for examination of RCU patients.