Thoracic imaging is regularly performed on the majority of critical care patients. Conventionally, this uses a combination of plain radiography and computed tomography. There is growing enthusiasm for the use of ultrasound to replace much of this radiology and provide more immediate, point-of-care imaging with reduction in patient transfers, ionizing radiation exposure and cost. This article explores the diagnostic performance of thoracic ultrasound in the imaging of pleural effusion, consolidation, extra-vascular lung water (EVLW), and pneumothorax. Current evidence suggests that, in expert hands, thoracic ultrasonography has similar diagnostic accuracy to computed tomography in pleural effusion, consolidation and pneumothorax. The technique also has potential to identify the cause of increased EVLW and accurately quantify pleural effusions. More large-scale studies are required in these areas however. Ultrasonography outperforms bedside chest radiography in all cases.