The radiologic evaluation of the solitary pulmonary nodule (SPN) is a common diagnostic dilemma. Although available clinical data and findings on conventional radiographs are important components in determining the imaging approach to the SPN, evaluation with CT often is necessary for detailed evaluation. This article reviews the radiologist's approach to the evaluation of the SPN, with a particular focus on the role of thin-section CT for morphologic and density analysis. The relative use of contrast-enhanced CT and nuclear medicine, particularly positron emission tomography, in detecting nodule enhancement is discussed. If the use of low-dose helical CT for screening for early lung cancer in the form of a SPN becomes widespread practice, it is likely that radiologists will encounter an increasing number of smaller SPNs in the near future.