Background:The diffuse panbronchiolitis (DPB) complicated with thymoma is very rare, only few cases have been reported. DPB is usually diagnosed by typical clinical features and radiological manifestations, our case had pathological evidence simultaneously.Case presentation:A 27-year-old male smoker presented with intermittent cough and mucoid sputum for about ten years which deteriorated for the last six months with intermittent fever, increasing fatigue and exertional dyspnea. Initially the weakness did not prevent him from engaging his work and everyday life. But it progressed to the point of unable to walk by himself nor to expectorate. No sweating, weight loss, or other systemic symptoms were noted. The patient had a history of sinusitis.Treatment: Following the diagnosis, pyridostigmine bromide, 60mg four times a day andRoxithromycin, 150mg once daily had been administered. Three months after the operation,follow-up CT scan showed no evidence of thymoma replase. Besides, centrilobular nodules werereduced.Discussion DPB is a disease of unknown etiology, in which genetic predisposition andimmunological derangement may all play a part. Neutrophils, T-lymphocytes, particularly CDB+cells, together with interleukin-8 and macrophage inflammatory protein-1(MIP-1)，are believed toparticipate in its development. When DPB and thymoma, occur in one patient, whichever comesfirst, immunological interaction is the most plausible hypothesis. Others assume that coexistenceof DPB and thymoma might be associated with lymphoproliferative disorders.Conclusion:This is a histologically confirmed DPB in a young patient with thymoma, which wasresponsive to macrolide. The interrelationship between these two diseases is yet to be defined.