Clinical studies conducted by the authors on 802 patients demonstrated that using of a combination of several known markers (CEA, CYFRA 21–1 and SCC) for NSCLC and (ProGRP, NSE, CEA or CYFRA 21-1) for small-cell lung cancer (SCLC) allow reaching Sen=80% in LC patients with Sp = 92% at Stages I-III. The gene discussed is CEACAM5; the disease is small cell lung carcinoma.