AIMS AND BACKGROUND: Small cell lung cancer (SCLC) is a chemotherapy-responsive tumor and associated with alterations in the coagulation system. Addition of low-molecular-weight heparin (LMWH) to combination chemotherapy (CT) had resulted in increase in survival. The present retrospective trial was designed to determine whether the duration of dalteparin usage has an effect on progression and survival. MATERIALS AND METHODS: The medical records of 67 patients with SCLC who were given cisplatin-etoposide and concomitant LMWH (dalteparin) was evaluated retrospectively. RESULTS: Median follow-up of patients was 11.3 months. Outcome: 10.6% complete response, 3.0% good partial response, 36.4% partial response, 10.6% stable disease, and 39.4% progressive disease. Side-effects were seen in 40.3% of the patients. Median dalteparin duration was 6,1 months. According the duration of dalteparin patients were grouped in three: who took dalteparin less than 4 months (Group A), 4-6 months (Group B) and more than 6 months (Group C). Mean overall survival (OS) in Group A was 6.5 months, in Group B 11.8 months, and Group C 14.6 months. Mean OS in Group B and C were statistically significantly (P < 0.001) longer than Group A, between Group B and C there was not any significant difference (P = 0.037). Mean progression free survival (PFS) was 9 months. CONCLUSIONS: The CT plus LMWH minimum 4 months long is well-tolerable, and may improve PFS and OS in patients with SCLC. For treatment of patients with SCLC CT plus LMWH may be considered as effective future-therapy, and further multi-centre randomised prospective clinical trials must be done to determine the new standard treatment approach for SCLC.