Collagen−vascular diseases (CVD) involve many organs. Among organ involvements, pulmonary disorders may determine the prognosis of CVD. Because the vasculature and blood perfusion are commonly altered in CVD, we have attempted to analyze pulmonary disorders from the viewpoint of pulmonary vessels and perfusion. Based on routine pulmonary function tests, many patients were observed to have a decreased diffusion capacity (DLco) isolated from or comparative to lung volumes. In these patients, matched ventilation/perfusion scintigraphy revealed a decrease in pulmonary peripheral perfusion. These findings may be an early sign of pulmonary hypertension, which develops as a result of several pathophysiological causes in CVD. When a remedy for each pathogenesis of pulmonary hypertension was applied, more than half the patients recovered, at least initially; therefore, early diagnosis, including the methods described above, and treatment are important. With regard to pneumonitis in amyopathic dermatomyositis, which has been considered to develop acutely, we observed its progression to be subacute in its early stage. Along with this disease, pneumomediastinum characteristically develops simultaneously with vasculopathy. Disease-modifying antirheumatic drugs, which must be perfused into the blood stream, sometimes induce lymphocyte alveolitis or pneumonitis in good responders, with a decrease in the peripheral blood lymphocyte count and immunoglobulin levels. Examinations, differential diagnoses, therapies and studies from the viewpoint of the blood circulation and vessels may be important and useful for clinical studies and for the further investigation of pulmonary involvement in CVD.