The respiratory and the renal systems are closely related both in health and in certain pathologic states. The purpose of this work was to study changes in pulmonary functions that accompany chronic renal diseases with different degrees of renal reserve and to evaluate the role of dialysis on such changes.42 spirometric tests were performed in 38 patients with chronic renal disease, their age range was (8 – 15 years). The patients were divided according to their renal reserve into 3 groups; (A) Normal renal reserve; GFR >75ml / min / 1.73m2 (10 patients) (B) Limited renal reserve; GFR 25- 75 ml / min / 1.73m2 (11 patients) (C) Consumed renal reserve; GFR <25 ml / min / 1.73m2 (17 patients). The last group was further divided in to 2 subgroups; (a) 7 patients receiving conservative treatment (b) 10 patients on regular HD, 4 of them were tested before being on regular HD. There was a significant decrease in FVC & FEV1 in group C (p< 0.05) indicating a restrictive defect. Also, there was a significant improvement in FVC and FEV1 after 3 months of regular HD. We concluded that affection of PFTs is not uncommon in patients with chronic renal disease and restrictive ventilatory defect is the commonest pattern of such affection. Critical values for GFR and Hb were suggested for prediction of patients likely to have affected PFTs.