Lung cancer, the most frequent cancer worldwide, is the fourth most frequent cancer in France, with an overall 5-year survival rate of about 15%, directly correlated to the stage of disease at the time of diagnosis and its treatment. The objective of this article is to describe the role, contributions and pitfalls of computed tomography (CT) in clinical TNM staging, primarily to identify patients eligible for curative surgery. TNM staging criteria, last updated in 2009, are discussed along with the new proposals for the 8th edition to be published late 2016. The most crucial CT features for pre-therapy assessment are highlighted.