Background- To date there are very few studies evaluating the relationship between sedentary behaviour and pulmonary function in a population who works for more than half a day i.e. 6-8hrs continuously in front of technologies (mainly desk jobs) with no sign of physical activities. Hence the aim of the study was to evaluate the effects of a sedentary lifestyle on peak expiratory flow rate. METHOD- The study was conducted on 75 desk job workers, males and females of age group 30-45 years working for 6-8 hours without physical activity. Analysis of their lung function capacity was done by PEFR. RESULT-It is seen that there is a significant difference in the predicted and obtained values of PEFR in both genders. The mean predicted value of PEFR in females is 416.04±25.72 and the mean obtained value of PEFR is 284.7±72.84. In males the mean predicted value of PEFR is 542.6±23.33 and the mean obtained value of PEFR is 396.2±80.6. It shows that the sedentary lifestyle with physical inactivity affects the PEFR values CONCLUSION-Regular exercise in terms of physical activity is essential for every individual with a sedentary lifestyle to overcome health problems and improve their pulmonary functions.