Abstract: <b<objective</b< To discuss imaging appearance of benign and malignant disease of solitary pulmonary nodule(SPN) and characteristic of diagnosis. <b<Material and Methods</b< 17 patients with pathologically-proved pulmonary nodule (diameter<3.0cm),including males 11cases and females 6 cases with the age of 38-83years (average 63.2 years).using helical CT scan with PQ5000,in them 7cases do contrast CT scans,5 cases do three dimension configuration. <b<Results</b< among 17 cases, malignant disease is 12 cases, benign disease is 5 cases,in malignant disease adenocar-cinoma is 8 cases and squamous-cinoma is 2 cases,in benign disease tuberculosis is 3 cases, inflammation node is 2 cases, the common CT signs included lobulation sign (14 cases),pleural tail sign(7 cases),vessel convergence (8 cases),and spiculation (14 cases),with inhomogeneous (13 cases). <b<Conclusion</b< CT scans about pulmonary nodus have important value in differentiate benign and malignant disease.