The aim of this study was (i) to determine predictive factors of a complete response to chemotherapy in small cell lung cancer (SCLC) and predictive factors of an objective response in non-small cell lung cancer (NSCLC) and (ii) to determine whether prognostic factors are different with regard to treatment response and survival. Ninety-nine patients with SCLC and two hundred and two patients with NSCLC received chemotherapy. The following variables were recorded prior to treatment: tumor, node, metastasis status, performance status, body weight loss, blood leukocyte count, serum sodium, serum albumin, lactate dehydrogenase (LDH), alkaline phosphatase, serum NSE, serum TPS, and serum CYFRA 21-1. Tumor response was analyzed at the 10th week. Analysis of survival were done using the landmark method. Hazard ratios of the significant prognostic variables of survival were calculated using the Cox's model. Odds ratios of the significant predicting factors of response were calculated by stepwise logistic regression. In SCLC, the significant determinants of poor survival were: lack of complete response (HR: 2.04), weight loss (HR: 1.76), high serum LDH level (HR: 1.64), and high serum TPS level (HR: 2.47). A high serum TPS level was the only factor among those studied able to predict lack of achievement of complete response (OR: 0.39). In NSCLC, significant determinants of poor survival were: no objective response (HR: 2.28), poor performance status (HR: 2.52), presence of metastases (HR: 1.51), and high serum CYFRA 21-1 level (HR: 1.84). On the other hand, a high serum TPS level (OR: 0.50), the presence of metastases (OR: 0.45), and a leukocyte blood count over 10,000/microl (OR: 0.43) were independent determinants for a patient not to achieve an objective response. We concluded that the predictive factors of complete response in SCLC remain to be defined. On the other hand, in NSCLC three variables contribute to the prediction of an objective response. Finally, determinants of survival differ from predictive factors of response.