A 31-year-old man experienced chest pain, fever, bloody sputum and cough after diet therapy. Chest radiography and chest CT showed infiltration in the right lower lung field and right pleural effusion. Pulmonary embolism and infarction was diagnosed using 99mTc-MAA perfusion scans and chest enhanced CT. The patient did not have a thrombotic disposition and deep vein thrombosis in the lower extremities. This case did not have an acute onset or dyspnea, and was not typical of pulmonary embolism. The diet therapy may have caused dehydration and acted as a predisposing cause of pulmonary embolism.