It is well known that respiratory functions are affected at clinical hypothyroidism. Simple spirometry which is a cheap and simple method is performed to the patients with subclinical hypothyroidism in order to determine if respiratory functions are affected or not. Recently diagnosed 87 patients with clinical hypothyroidism, 120 patients with subclinical hypothyroidism and 60 healthy subjects were enrolled in the study. Serum plasma levels of fT3, fT4 and TSH were measured and spirometry test is performed to healthy subjects and patients with clinical and subclinical hypothyroidism. There was a significant difference when groups with subclinical and clinical hypothyroidism were compared with control group. The comparison of subclinical and clinical hypothyroidism revealed a slight elevation at all of the spirometric parameters in favor of subclinical hypothyroidism which did not reach statistical significance (p> 0.05). Respiratory functions may be affected in patients with subclinical hypothyroidism as it is with clinical hypothyroidism; therefore we think that recommend community screening for respiratory functions in patients who may be at risk of subclinical hypothyroidism may be helpful.