Background: In a retrospective study files of 96 non-operated, non-small-cell lung cancer (NSCLC) patients receiving radiation therapy were statistically analysed. A correlation of the pre-therapeutical haemoglobin level and the survival of patients after a primary radiation therapy has been described by some authors, but it is an open question whether there is any dose-modification in the treatment schedule, related to different prognostic subgroups of patients, that makes sense., Patients and Method: We have analysed the files of 96 primary radiated patients to evaluate the pre-therapeutical haemoglobin level as well as sex, age, histopathology, total dose and fractionation. The analysis of Karnofsky-status or patient condition was not performed as there was a lack of sufficient data in the patient files., Results: Histopathology, sex, age as well as total dose and fractionation of the radiation treatment were similar in the cohort building 3 groups: Hb < 11 g/dl, Hb between 11 to 15 g/dl and Hb > 15 g/dl. The investigation resulted in the observation, that lower levels of initial serum haemoglobin concentration compared to levels over 15 g/dl are negative prognostic factors. Higher initial haemoglobin concentration is a high significant positive prognostic factor (p = 0.0001). The applied total dose (> 30 Gy, > 50 Gy, > 55 Gy) was not a significant prognostic factor in this patient material, where two thirds of the patients had an advanced cancer (stage IIIB or stage IV)., Conclusions: We conclude that initial haemoglobin concentration is a significant prognostic factor for NSCLC patients treated by radiation therapy. Further investigations are necessary to determine whether a dose escalation can improve the outcome of a subgroup of patients with high-normal haemoglobin levels.