A 53-year-old man had received various chemotherapy and steroid treatments for malignant thymoma. He had demonstrated persistent fever since the beginning of January 2006, and chest radiograph showed consolidation in the left middle lung fields. Bacterial pneumonia was suspected, but antibiotics were not effective. He was referred and admitted to our hospital on January 16. Chest radiograph and CT scan on admission showed diffuse ground-glass opacities, consolidation with cavity, and cystic changes. Pneumocystis jiroveci Pneumonia was diagnosed by examination of alveolar lavage. This patient was regarded as immunodeficient because of steroid treatment, low counts of CD4-positive lymphocytes, and the complication of hypogammagloblinemia. We reported this case of a non-HIV patient with atypical images demonstrating Pneumocystis jiroveci pneumonia.