Objective: Although it has been well established that hypertension effects pulmonary functions negatively, the effect of regular antihypertensive therapy on pulmonary functions is not known. In this study, we aimed to compare the pulmonary function tests of the hypertensive patients taking regular antihypertensive therapy with those of the ones not taking any antihypertensive medicine, to document the differences in pulmonary functions of both hypertensive groups. Materials and Methods: Patients who had received antihypertensive treatment (Group I: 29 males, 24 females, mean age 42.3 +/- 8.2 years), and untreated cases (Group II: 28 males, 22 females, mean age 43.4 +/- 6.4 years) were included in the study. Patients with a history of coronary heart disease, respiratory diseases, smokers and those who were obese were excluded from the study. Results: Forced vital capacity (FVC) and forced expiratory volume at the first second (FEV1) levels were found significantly lower in Group II ( p < 0.05). In echocardiographic evaluation, the mitral E/A ratio of Group II was lower than that of Group I ( p < 0.05). Isovolumetric relaxation time and deceleration time was higher in Group II than in Group I ( p < 0.05). There was a significant association between pulmonary function tests and impaired left ventricular diastolic parameters; especially, mitral E/A ratio was significantly associated with decreased FVC and FEV1 in Group II (respectively r = -0.695, p = 0.01 and r = -0.591, p = 0.03). Conclusion: FVC and FEV1 levels in untreated hypertensive cases were lower than in those of treated hypertensive cases, and this may be caused by diastolic function rather than the systolic function. In the evaluation of dyspnea in hypertensive patients, it would be useful to examine respiratory function in addition to echocardiographic investigation.