Late-onset noninfectious pulmonary complications (LONIPC) occurring after allogeneic hematopoietic stem cell transplantation (HSCT) represent a heterogeneous group of pulmonary diseases, including bronchiolitis obliterans syndrome (BOS) and interstitial lung diseases (ILD). This chapter focuses on post-HSCT ILDs. According to the international consensus for idiopathic ILDs, almost all types of ILD except usual interstitial pneumonia and desquamative interstitial pneumonia have been found after HSCT. Many of these diseases have similar presentations to their idiopathic forms or may be associated with systemic symptoms such as those of connective-tissue diseases. Hence, when evaluating a patient with a post-HSCT ILD, using a systematic approach similar to the one used in evaluating any patient with ILD can be useful. Most of ILDs occurring after HSCT are associated with extrathoracic manifestations of chronic graft-versus-host disease (cGVHD). Whether ILDs belong to the spectrum of lung GVHD, such as bronchiolitis obliterans, is still under investigation. The concept of restrictive allograft syndrome (RAS) has recently emerged after HSCT, based on a functional respiratory definition, as opposed to the obstructive ventilatory disorder that characterizes BOS. ILDs are a cause of these RAS. The management of ILDs mainly relies on corticosteroid therapy, with the exception of pleuroparenchymal fibroelastosis. Although the management differs, the prognosis of ILDs is similar to that of BOS.