Lung cancer (LC) is the leading cause of cancer mortality worldwide, predominantly due to the difficulty of early diagnosis and its high metastatic potential. Recently, increasing evidence suggests that circulating tumour cells (CTCs) are responsible for cancer metastatic relapse, and CTCs have attracted interest in cancer metastasis detection and quantification. In present study, we collected blood samples from 67 patients with bone metastasis, and 30 patients without such metastasis, and searched for CTCs. Then the association of CTC numbers with bone metastasis and other clinico-pothological variants was analyzed. Results demonstrated that when 5 or 1 was taken as a threshhold for the CTC number, there were significantly higher positivity of CTCs in the bonemetastasis group than in the non-metastasis group. While the increase in CTC number was not significantly associated with any other clinicopathological factor, including age, gender, pathological type, intrapulmonary metastasis and lymph node metastasis, the CTC number in patients with positivity of the last above mentioned variants was obviously higher than in patients with negativity of the two variants. Taken together, the CTC number appears to be significantly associated with the bone metastasis from lung cancer.