This study was designed to elucidate the possible relationship between the expression of cytosolic carbonic anhydrase (CA) and non-small cell lung cancer (NSCLC). The activity and protein expression patterns of carbonic anhydrase I (CAI) and II (CAII) of 70 NSCLC patients were analyzed by CA activity analysis, immunoblotting and immunohistochemical staining. The results showed that the CA activity and protein expression were significantly decreased in both squamous cell carcinoma (SCC) and adenocarcinoma (AD) (P<0.001 and P<0.001). From our study, it was suggested that the reduction of CAI and CAII in both SCC and AD patients may promote tumor cell motility and contribute to tumor growth and metastasis.