Two hundred fifty patients who had 240 pathological changes of the lungs or mediastinum were examined using both scanned projection radiography (SPR) and standard film radiography, and the diagnostic accuracy of the procedures was compared. The use of standard film radiography led to diagnostic findings in 90.1% of the cases, while 94% of the images obtained at SPR provided diagnostic findings. The equivalent performance and, in part, the slight superiority obtained with the digital technique is a result of the better contrast resolution for objects with diameters greater than 2 mm. A further improvement in the diagnosis of thoracic disease with digital radiography may occur because of the use of special mathematical algorithms for image reconstruction and with the use of dual-energy subtraction radiography rather than by an increase of spatial resolution.