Many studies proved the efficacy of vertical banded gastroplasty (VBG) in weight reduction. However, few have dealt with its impact on efficiency of respiration and on pulmonary function tests (PFTs). The aim was to obtain a numerical assessment of the effect of VBG on different PFTs. The study included 21 morbidly obese patients (BMI>40kg/m2). All patients had PFTs preoperatively and six months following VBG. Changes in the mean weight, body mass index (BMI) and PFTs were analyzed using paired t test. Correlation between BMI changes and changes in PFTs was also analyzed. Six month following VBG there was a significant BMI reduction from a mean of 49.6 to 38.01kg/m2 (P<0.00001). There was a highly significant improvement in restrictive pulmonary dysfunction represented by changes of mean SVC from 3.13 to 3.33L (P=0.005) and mean FVC from 3.07 to 3.33L (P<0.00001). There was also a significant improvement in obstructive pulmonary dysfunction represented by changes of mean FEFmax from 5.58 to 6.12L/s (P=0.00001) and mean FEV1 from 2.54 to 2.81L (P=0.0001). Overall lung performance significantly improved as evidenced by elevation of ERV from 0.63 to 0.93L (P=0.00004). MVV, which reflects work of breathing, did not show a significant change. It changed from a mean of 83.0 to 77.57L/m (P=0.05). There was no statistically significant correlation between the improvement in BMI and the above-mentioned PFTs changes within a period of six month. Besides the efficacy of VBG in weight reduction, it produces highly significant improvements in both restrictive and obstructive PFTs, as well as overall lung performance, in a period of six month. It, however, produces no significant change in the work of breathing.