Objective: The aim of this study was to investigate the correlations among symptoms, laboratory findings of bone metastasis and whole body bone scanning (WBBS) and the frequency of occurrence of bone metastases materials and methods:Hundred and six patients who were diagnosed with non-small cell lung cancer (NSCLC) between June 2001 and September 2005 were investigated retrospectively. Bone pain, detection of bone tenderness on physical examination, hypercalcemia and increased serum alkaline phosphatase were accepted clinical factors of bone metastases. Presence of multiple asymmetric lesions in WBBS was also accepted as bone metastases. Subjects whose clinical factors and WBBS indicated doubtful bone metastases were evaluated with magnetic resonance and/or biopsy. Results:Occurrence of bone metastases was 31.1% among all patients. Bone metastases were determined in 21 (52.5%) of 40 patients who had at least one clinical factor. Asymptomatic bone metastases without any clinical factors were established in 11.3% of all NSCLC patients and 15.3% of 26 operable patients. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the clinical factors of bone metastases were 63.6, 73.9, 52.5, 81.8 and 70.7% respectively. There was no significant relationship between histologic type and bone metastases. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of WBBS in detection of bone metastases were 96.9, 86.3, 76.2, 98.4, 89.6% respectively. Conclusion:Sensitivity and specificity of the clinical factors of bone metastases are quite low. Routine WBBS prevented futile thoracotomies. Therefore, routine WBBS should be performed in all NSCLC patients, even in the absence of bone-specific clinical factors.