Technical details of volumetric spiral CT and high resolution CT are presented. The role of CT scan in lung cancer is discussed: confirmation of a suspected lesion, identification of an unknown one, clinical staging, planning bioptic procedures and follow-up. In clinical staging, CT scan measures tumor diameter and relationship with surrounding structures (T factor) as well as investigates about nodal status (N factor) at the hilum or in the mediastinum but the limitation is due to the difficulty of distinguish between nodal inflammatory enlargement and metastatic involvement. Moreover, CT can be extended to the upper abdomen aimed of assessing adrenals, kidneys and liver (M factor).