Background : Smoking reduces the ability of the lungs to function. In particular, smoking reduces the vital capacity of the lungs, which is the amount of air the lungs can take in. This reduction in vital capacity has several important health effects. Purpose : The purpose of this study, therefore was to examine the effects of the respiratory muscle exercise on peak expiratory flow and respiratory muscle strength. Methods : For an experimental research design, it was employed 20 young healthy subjects and these subjects were assigned into two groups; a smoking group(n=10) and an non-smoking group(n=10). All groups were participated in respiratory muscle exercises twice a week for 5 weeks in same condition. For comparison between before and after for post treatment, it was analysed as paired t-test and ANCOVA. Results : The result of this study were as follows; In the case of smoking group, there were significant differences, from $427.77{pm}76.61$ l/min to $526.66{pm}58.52$ l/min of peak respiratory flow, from $94.33{pm}22.07$ kg to $102.16{pm}21.60$ kg of abdominal muscle strength between the before and the after of respiratory muscle strength exercises. In the case of nonsmoking group, there were significant differences, from $449.54{pm}77.47$ l/min to $553.18{pm}61.32$ l/min of peak respiratory flow, from $93.41{pm}19.21$ kg to $101.58{pm}18.92$ kg of abdominal muscle strength between the before and the after of respiratory muscle strength exercises. Conclusion : These results were suggested that the peak respiratory flow and muscle strength were improved after respiratory muscle strength exercises.