This review focuses on the clinical use of $^{18}F-FDG$ PET to evaluate solitary pulmonary nodule (SPN) and non-small cell lung cancer (NSCLC). When SPN or mass without calcification is found on chest X-ray or CT, $^{18}F-FDG$ PET is an effective modality to differentiate benign from malignant lesions. For initial staging of NSCLC, $^{18}F-FDG$ PET is useful, and proved to be cost-effective in several countries. $^{18}F-FDG$ is useful for detecting recurrence, restaging and evaluating residual tumor after curative therapy in NSCLC. For therapy response assessment, $^{18}F-FDG$ PET may be effective after chemotherapy or radiation therapy. $^{18}F-FDG$ PET is useful to predict pathological response after neoadjuvant therapy in NSCLC. For radiation therapy planning, $^{18}F-FDG$ PET may be helpful, but requires further investigations. PET/CT is better for evaluating NSCLC than conventional PET.