Diabetes mellitus is a public health problem in developing and developed world .The great attention was centered on the diabetic complications like cardiovascular, nephropathy, retinopathy and neuropathy. The pulmonary complications of type-2 diabetes mellitus have been poorly characterized. Several studies are suggested that diabetes is associated with impaired pulmonary functions. The underlying mechanism seems to be microangiopathy brought in by the non enzymatic glycosylation of various scleroproteins in lungs and elsewhere. Since collagen is the most abundant tissue protein in major bronchi, vessels and interstitium, the alterations in pulmonary functions occur as a rule. The aim of the present study is to assess the effects of chronic hyperglycaemia on lung functions, which focused on mechanical aspects of lung dysfunction – maximal forced spirometric pulmonary function tests like FVC, FEV1, PEFR, FEV1/FVC% to be specific.