Single photon emission computed tomography (SPECT) of the lung was performed, in addition to conventional camera scintigraphy, in 41 patients with pulmonary disorders as well as with regular pulmonary perfusion. For SPECT investigation a rotating gamma camera (Gammatome) was used consisting of a system with a high-resolution parallel-hole collimator interfaced with a digital computer. In 6 of 41 patients the diagnostic accuracy of pulmonary scintigraphy was improved by SPECT. Topographic identification of segmental perfusion defects in pulmonary embolism seems to be particularly promising. Special abnormalities that cannot be assessed by conventional lung imaging are mediastinal hernia and recessus retrotrachealis as a normal variant. For a detailed evaluation of this method a large number of patients must be investigated.