The aim of our study was to evaluate the usefulness of serum OPG and ProGRP during chemotherapy of lung cancer in relation to the histological type of the tumour, its clinical stage and the response to therapy. The levels of OPG and ProGRP were determined in 39 patients (20 NSCLC, 19 SCLC) and 10 healthy subjects. Blood samples were collected from each patient before and after chemotherapy. OPG and ProGRP levels in all the patients with lung cancer were higher than those in the controls. ProGRP were higher in SCLC group than in those NSCLC. In NSCLC group (after chemotherapy), OPG level in patients with Stage IV tumour was higher than in those with Stage IIIB (p=0.03). OPG in ED SCLC were higher than those in LD SCLC (p=0.04). In SCLC group, ProGRP were higher in LD patients than those with ED (p=0.04). Concluding, the measuring of OPG and ProGRP in lung cancer patients may be useful in clinical practice.