I read with interest the article by Verdial and colleagues 1 published in The Annals of Thoracic Surgery. The authors' aim was to develop a prediction model for nodal disease as a potential alternative approach to staging. For this purpose, they constructed a logistic regression model to estimate the probability of nodal disease in a very good manner, and they selected variables and parameterizations to maximize discrimination. In addition, for evaluation of the model performance, discrimination and calibration were used.This study is valuable and important, but some important comments are recommended in this regard. Validation is one of the most important stages in building the model prediction. In doing this, data should come from 2 different cohorts, but if it is from a single cohort, data should be divided into 2 parts. The first part is used for developing the prediction model and the second part is used for developing the validation model. The main results obtained from model development may be misleading if the validity of the model is not appropriate. [2][3][4] Given these comments about prediction models, the authors' results should be interpreted with caution.