Objective To explore the CT appearance of thoracic lymphonodus in AIDS patients with immune reconstitution in-flammatory syndrome(IRIS)after highly active antiretroviral therapy (HAART).Methods The data of thoracic CT in 24 AIDS pa-tients after HAART with enlarged thoracic lymphonodus in IRIS were collected,and the chest CT appearance was analyzed.Results Of the 24 cases of AIDS patients with IRIS after HAART,1 9 cases were complicated with pulmonary tuberculosis,which includ-ed 5 cases with cervical tuberculous lymphadenitis,3 cases were co-infected with bacterium and fungi,1 case was infected by penicil-lium marneffei,1 case by pneumocystis carinii.The enlarged thoracic lymphonodus were primarily located in 4R region(20/24), secondly in 2R region(1 1/24)and 4L region(1 1/24),in which the density was uniform or non-uniform,edge clear or unclear,some parts of lymphonodus were fused together but not calcified.The minor axis of enlarged lymphonodus was 1 1.0-25.0 mm except X region,enhanced uniformly in 2 cases.Obstructive pneumonia and pulmonary consolidation were found in 2 cases with enlarged lym-phonodus,which were located in 10R region.Pleural effusion was found in 13 cases with greatest depth of about 22 mm,pericardial effusion was found in 5 cases with greatest depth of about 24 mm.Conclusion The enlarged thoracic lymphonodus in AIDS patients with IRIS affer HAART are mainly involved in the region of 4R,2R and 4L,with or without pleural effusion and pericardial effusion.