Abstract
Background: Smoking remains the most preventable cause of premature death and morbidity in the US and the developed world. Cigarette smoking is the most well known risk factor for accelerating lung function decline in adults. This study aimed to evaluate pulmonary function tests abnormalities predictors in smoker patients

Materials and methods: This case-control study was done in Merjan teaching Hospital, Babylon, Iraq, in the period from December 2010 to March 2012. The study included 182 patients who were divided into 114 patients in obstructive group and 68 patients in restrictive group. Duration and amount of smoking were evaluated by pack years. Spirometry was done for each patient. The effects of smoking were compared between obstructive and restrictive chronic lung diseases.

Results: The ages of patients in both groups ranged from 31-70 years. Most of patients were males (65% in obstructive group while 58% in restrictive group). There was significant correlation between pack years and degree of dyspnea (functional state),in addition there was significant correlation between pack years and severity of obstructive and restrictive diseases.

Conclusions: The results of this study indicate that effects of smoking were more in obstructive group than restrictive group. It was established that lung function (FEV1,FVC and FEV1%FVC) decreases with increasing number of pack years. Lung function was related inversely to pack years of cigarette use