CD10 is a zinc dependent metallopeptidase, and its expression in stromal and/or epithelial cells of many carcinomas has been suggested to have prognostic value. This study investigates CD10 expression in epithelial and stromal cells of non small cell lung carcinoma (NSCLC), and evaluates its prognostic value for this tumor and its histologic subtypes. Sixty-six cases of NSCLC [35 cases of nonsquamous cell carcinoma (NSCC) and 31 cases of squamous cell carcinoma (SCC)] were analyzed immuno-histochemically for CD10 antibody. Fisher's exact test and univariate survival analyses were performed. Comparison of clinicopathologic characteristics for NSCLC showed that only stromal CD10 expression had worse prognostic impact, associated with the presence of recurrence (p = 0.001), death (p = 0.006) and disease positivity (p = 0.001). For SCC, CD10 was found to be expressed mainly in the stromal cells, and was associated with a decreased survival (p = 0.000) and disease free survival (p = 0.000). CD10 expression was restricted to the epithelial cells in NSCC and associated with an increased disease free survival (p = 0.036). Stromal CD10 expression apppears to be a worse prognostic factor in NSCLCs. CD10 which is expressed in different cell components of SCC and NSCC appears to have opposing effects on the behaviour of these histologic types.