Purpose To study the spiral CT (SCT) appearances of pleural plaques,to improve the accuracy of diagnosis and differential diagnosis,and to evaluate clinic application.Materials and Methods The SCT appearances in 42 cases with pleural plaques were analysed retrospectively,which closed met with asbestos dust.Results SCT showed 407 pleural plaques in 42 cases,of which there were hyline / uncalcified pleural plaques (n=250),calcified pleural plaques(n= 36),mixed pleural plaques(n=121);unilateral pleural plaques (n=10),bilateral pleural plaques (n=32);single pleural plaque in 5 cases,multiple pleural plaques in 37 cases.The largest pleural plaque was 4.2cm×1.2cm.There were a lot of shapes of the pleural plaques.Various shapes of calcifications could be showed in the calcified or mixed type pleural plaques.The pleural plaques distributed in the middle-inferior part,anterior / posterior-lateral chest wall,underlying the ribs in 28 cases (66.6 %),both bilateral domes of diaphragm in 10 cases and mediastinal pericardium in 4 cases.The pleural plaques associated with pulmonary intertitial fibrosis in 4 cases.No cases in the apices / costophrenic angles.No enhancement of pleural plaques in 6 cases which were administrated contrast scan.Conclusion SCT can clearly show the distribution,extention,shape,size,density and relation to adjacent tissues of the pleural plaques,and with asbestos exposure history,can make a diagnosis and differential diagnosis from other pleural thickened lesions.SCT is the best choice of imaging methods for asbestosis and pleural plaque.