Regional pulmonary blood flow (PBF), regional pulmonary extravascular water (PEW), and regional pulmonary blood volume (PBV) were measured quantitatively with positron emission tomography (PET) using H2(15)O and C15O in normal human subjects and patients before and after thoracotomy. The method was based on the Kety's model and a modification of the Mintun's method of measuring regional PBF with H2(15)O. The method consisted of intravenous injection of H2(15)O and dynamic PET scanning of the lung field and the right heart blood pool. Another scan following C15O inhalation was performed to visualize the blood pool, and the influence of the blood pool radioactivity to the H2(15)O image was subtracted. A mathematic model was applied to the data analysis, and the least-square fitting procedure was used with a computer for obtaining the optimal parameters. The mean values of the measured PBF, PEW, and PBV in two normal human subjects were 67.2 +/- 23 ml/min/100 ml, 17 +/- 5 ml/100 ml, and 19 +/- 6 ml/100 ml, respectively. The PBF, PEW, and PBV increased in the direction of gravity in the transverse cross-section image of the lung. Using this method, we studied the condition of patients who underwent lung surgery with thoracotomy. The PEW increased and the PBF decreased in the patients after surgery. This condition lasted for a few days, and the patients then recovered. The well-known phenomenon of pulmonary edema occurring after thoracotomy, which is usually recognized by symptoms and radiologically, was thus confirmed quantitatively by our method.