The levels of the new tumour marker CYFRA 21-1 were assessed in 115 patients with non-small cell lung cancer (NSCLC) and in 45 patients with non-malignant lung disease. Increased levels of CYFRA 21-1 were observed in 47.8%, mostly in patients with squamous cell carcinoma (SCC; 69.1%). Serum CYFRA 21-1 levels were correlated with the stage of SCC type. Positive CYFRA 21-1 levels in patients with SCC were present in 40% of stage I, 61.1% of stage II, and 85.2% of stage III. In addition, SCC patients who presented mediastinal lymph nodes (N2) demonstrated higher serum CYFRA 21-1 levels, compared with patients without mediastinal lymph nodes metastases (N0 or N1). With regard to tumour size, significant difference was observed between T1, T2 and T3. The study also showed that the percentage of patients who survived 18 months with normal preoperative level of CYFRA 21-1 was higher compared with those patients with elevated preoperative levels of this marker, but the differences were not statistically significant.