Our purpose was to review the reported behavior and malignant risk of small noncalcified pulmonary nodules detected by computed tomography (CT). A review of published clinical guidelines and studies using CT scan for lung cancer screening was performed. Small pulmonary nodules are found in 5 to 60% of patients in published CT screening studies. The detection rate is influenced by the CT scan technique used, definition of a significant nodule, and the population of subjects screened. There is limited published systematic longitudinal observation of all nodules of any size. The malignancy rate of small nodules detected in smokers is likely less than 1 to 2%, and predictors of malignancy include semisolid appearance, diameter greater than or equal to 10 mm or persistent growth on greater than or equal to two CT scans. There is a wide variation in the performance of positron emission tomography (PET) scan in screening detected lung cancers. In summary, multidetector row CT detects greater than or equal to 1 nodule in most high-risk patients. The risk of malignancy for a single nodule appears to be low, but is increased by serial growth, diameter greater than or equal to 10 mm, and semisolid appearance. The role of PET in evaluating these nodules needs further exploration. Serial follow-up for 24 months in a high-risk cohort appears reasonable based on present data, but further longitudinal information is required.