Cryptogenic organizing pneumonia (COP) is a distinct clinico-pathologic entity described for the first time by Davison in 1983 and 2 years later by Epler under the name of idiopathic Bronchiolitis Obliterans Organizing Pneumonia (BOOP). It most often presents with the clinical and radiological features of an infectious pneumonia which fails to respond to antibiotic therapy. In this article, we will review the clinical and radiographic features, diagnostic assessment, and the treatment of COP.