We now are detecting an increasing number of SPN that are difficult to diagnose. Many of the techniques we traditionally have relied on were developed when the average size of detected nodules was larger, and these techniques are of limited diagnostic usefulness for small nodules. In the past, recognition of the need for noninvasive differentiation between benign and malignant nodules led to the development of many useful diagnostic techniques. The ever increasing number of small nodules now being detected will stimulate new approaches. In the future, as in the past, many of these will be based on previously developed concepts. Because a majority of these small nodules will be benign, it will be important to develop reliable methods of determining which patients need further evaluation both from a patient management and cost-effectiveness perspective. Criteria will need to be developed based on the initial CT appearance of the nodule, clinical information about the patient, and subsequent CT using the latest decision analytic techniques and databases. Finally, increased interest in predicting the aggressiveness of a lung cancer, once it has been discovered, could lead to further changes in staging criteria.