purpose: to analise the sensitivity, specificity, and positive and negative predictive values of the computerized axial tomography (ct) in nodal stages of lung carcinoma. material and methods: thirty patients suffering from lung carcinoma were analysed between may 2003 and may 2004. ct screening of the thorax was made to all the patients. mediastinoscopy or lung resection samples plus systematic node dissection were performed, and the efficiency of ct analysed by comparing the obtained data with the histopathology results of nodal affection shown by mediastinoscopy and lymph node dissection. results: the sensitivity, specificity, and positive and negative predictive value of the computerized axial tomography (ct) for nodal staging involved in lung carcinoma were 72.2%, 100%, 100% and 70,6% respectively. conclusions: ct of the thorax is considered a usual imaging technique in lung carcinoma diagnosis; but in some cases it does not focalise correctly the nodal staging involved in lung carcinoma. in theses cases, it is necessarry to perform invasive techniques such as mediastinoscopy. at present, positron emission tomography (pet) is the technique that better permits to focalise the tumor offering the best data for the therapy of each patient, and avoiding invasive diagnosis techniques.