OBJECTIVE: To determine the association of type 2 diabetes mellitus with smoking at tertiary care hospital. PATIENTS AND METHODS: This comparative cross sectional study of six months was conducted at tertiary care hospital at Hyderabad. The inclusion criteria of the study were fifty smokers of ≥35 years of age and either gender had history of smoking ≥ 5 years while fifty non cross sectional of same age group were also recruited as control group. The history was taken regarding the age for stating of cigarette smoking, number of cigarettes smoked per day, current smoking or ex-smoker and total duration of smoking. In known type 2 diabetic patients detailed history was taken regarding age at the time of diagnosis, medications used and whether the disease was controlled or not. Blood glucose was done in the pathology laboratory or by glucometer and other routine investigations were also carried out if required. RESULTS: During six months study total one hundred individuals (fifty smokers and fifty non smokers) were evaluated for diabetes mellitus. The mean age ±SD for whole smoker and non smokers was 50.98±7.86 and 48.84±8.63 with male gender predominance. In smoker group the diabetes was detected in 34 (68%) patients while in non smokers the diabetes was identified in 12 (24%) individuals. The association is directly proportional to number of cigarette smoke and duration of smoking. CONCLUSION: The smoking is an independent risk factor for type 2 DM and observed in both the genders. The longer the duration of smoking, the more chances of developing type 2 diabetes mellitus. KEYWORDS: Smoking, Type 2 diabetes mellitus, Diabetes mellitus