A rapid response to corticosteroid treatment and a generally favourable outcome are characteristic features of BOOP (Bronchiolitis obliterans organizing pneumonia). However, with increasing experience of the clinical spectrum of this disease, it is now recognized that some patients are refractory to steroid, which is associated with a poor prognosis. Here, two cases of BOOP initially treated with predinisone and antibiotics without effects, but subsequently responded to secondary cyclosporine treatment, are reported.