The possible relationship between the severity of obesity and the ventilatory function parameters among Saudi male children has been investigated. In addition to comparing the ventilatory function of of Saudi male children with different body weights to their age matching Caucasian reference values. Healthy Saudi male school children participated in this study. Selected children were divided into three groups, group I (normal weight children), group II (overweight children), and group III (obese children). Ventilatory function tests were conducted using portable Spirometer. Comparing the ventilatory function of the three groups of Saudi children showed that increasing degree of obesity have negative effect on ventilatory function among Saudi children as the ventilatory function of the obese Saudi children were much lower, than their age matching overweight and normal weight Saudi children but with non statistically significant differences between the three groups. Statistical analysis of the data also showed that Saudi children have ventilatory function much lower than the predicted reference values based on the age/sex specific BMI percentiles. Conclusion: Over weight and obese Saudi male children have much lower ventilatory function compared to their age matched normal weight Saudi children and their age matchedreference predicted values in away that could restrict their lung expansion and affect their exercise capacity.