Background: There are several studies on the effect of diabetes mellitus (DM) on clinical symptoms and radiological findings of multi- drug resistant tuberculosis (MDR-TB) and bacteriological findings in pulmonary tuberculosis patients. Considering the contradictory results of these studies, this study was conducted for further investigation in this regard. Materials and Methods: This was a case – control study conducted in Masih- Daneshvari Hospital in Tehran. Forty-seven patients with tuberculosis infection and diabetes type II were selected as the case group and 102 TB cases without diabetes were considered as controls. Results: There were significant differences in hemoptysis, dyspnea and loss of appetite between the two groups, but no significant difference was found in cough, sputum production, chest pain, night sweat, fever or weight loss. Also, there was no significant difference between the 2 groups in terms of MDR-TB and bacteriological findings. On CXR, diabetic patients had a higher prevalence of typical presentations along with cavitary lesion(s) but no significant difference was found between the 2 groups in terms of radiological presentation. Conclusion: In this study, diabetes type II did not have much influence on clinical symptoms and bacteriological findings of TB patients. However, PTB–DM type II cases may be considered more contagious due to the higher prevalence of cavitary lesions compared to those without DM. Prevalence of MDR-TB was the same in both groups.(Tanaffos 2010; 9(2): 13-20)