Idiopathic pulmonary hemosiderosis (IPH) is a rare respiratory disease with an unknown etiology, and is diagnosed with laboratory, radiology, and pathology tests. Chief complaints of IPH include hemoptysis, cough, and dyspnea. Since it is considered an immune-mediated disease, the first line of treatment is systemic corticosteroid therapy. The three cases reported here showed a decrease in ferritin level and improvement in the hemoglobin level with prednisolone treatment. However, long-term corticosteroid therapy may cause several side effects, particularly growth retardation and obesity, which can affect growing children. In the present study, all patients had cushingoid symptoms and obesity. Therefore, we switched to deflazacort (DFZ), which has lesser side-effects of weight gain. This report describes clinical courses of the disease and comparison of body mass index of three patients with IPH who took DFZ instead of prednisolone. DFZ was effective for IPH, and is useful for weight gain reduction.