Background: Preoperative positron emission tomography/computed tomography (PET/CT) is recommended as a guideline for staging of lung cancer. However, for patients with pulmonary ground-glass opacity (GGO) nodules who are supposed to have a relatively low risk of incidence of lymphatic metastasis, it remains uncertain whether PET/CT is more effective than consolidation-to-tumor ratio (CTR) in the prediction of regional lymphatic metastasis. Methods: The data on patients who underwent surgery for lung cancer from 2011 to 2016 were collected retrospectively, which included CTR, results of PET/CT, and pathological characteristics. The patients who had undergone preoperative PET/CT were identified to find the risk factors for lymphatic metastasis. A receiver operating characteristic (ROC) curve and multiple logistic regression was utilized to clarify the predictive value of CTR and main tumor maximal standardized uptake value (SUVmax). Results: Among 217 patients who had PET/CT before lobectomy, chest computed tomography revealed that 75 patients had CTR greater than 62%. The patients with lymphatic metastasis were shown to have higher CTR and higher main tumor SUVmax. Multiple logistic regression showed that younger age (<60 years), higher main tumor SUVmax on PET/CT, and greater CTR were independent predictive factors for lymphatic metastasis. The area under the ROC curve was comparable, 0.817 for CTR, and 0.816 for main tumor SUVmax. Conclusions: The present study revealed that CTR was not inferior to main tumor SUVmax considering the predictive power for lymphatic metastasis preoperatively in lung cancer patients with a GGO component. PET/CT might not be necessary preoperatively in selected patients.