This retrospective study aimed at evaluating the prognostic impact of high serum levels of either the HER-2 extracellular domain (ECD) or the epidermal growth factor receptor (EGFR) ECD measured using two specific ELISAs in 221 patients with non-small-cell lung cancer (NSCLC) receiving conventional therapy and 41 nonmalignant pulmonary diseases patients. It was not possible to discriminate between lung cancer and benign lung disease owing to the lack of sensitivity-specificity relationship of HER-2 and EGFR ECD levels. Neither HER-2 nor EGFR ECD specific levels were associated with a particular prognosis of NSCLC patients receiving conventional therapy.