The main objective of this analysis is to evaluate the impact of lung cancer and diabetes association on cancer treatment and outcome of lung cancer patients. Lung cancer, as well as diabetes mellitus, are two diseases with very high prevalence. Lung cancer, despite the improvement in diagnosis and therapeutic methods, is still the 1st cause of cancer-related deaths. The influence of diabetes on cancer patients survival is well established among patients with hepatic, pancreatic or breast cancer. Diabetes implication on lung cancer outcome is not well known. Several studies reported a negative impact, whereas other studies reported a better prognosis for these patients. Our study took place in the Oncology Department of the Clinical Emergency Hospital of Constanta, Romania. 80 patients with diagnosis of non-small cell lung cancer were elected to participate in this study; 29 patients had also diabetes. Selected patients were divided in 2 groups, one group of lung cancer and diabetes, and one group without diabetes. Features of the patients among both groups were analyzed. Our study showed that preexisting diabetes is an unfavorable factor, and has influence on lung cancer prognosis, treatment adhesion and quality of life. To amend the outcome of patients with lung cancer, a better evaluation of patients� co-morbidities, including diabetes mellitus, is required.