Aim: A few previous studies reported contradictory results about the effects of reduction mammaplasty on pulmonary function tests. This study was conducted to evaluate the effects of breast size on pulmonary functions in volunteer healthy adult women that, to the best of our knowledge, was not reported before. Method: Ages, body mass indices, and underband and overbust measurements for breast sizes of 100 adult female volunteers without any known lung disease subjects were recorded. Differences between the overbust and underband measurements gave the cup sizes. Four groups were formed according to the cup sizes as: <6.5 cm (cup size A), 6.5 to 13 cm (cup size B), 13-19.5 cm (cup size C), and >19.5 cm (cup size D). Pulmonary function tests were performed to each subject Result: Pulmonary function tests did not show significant difference between groups. Difference of body mass index was significant between groups. Age, body mass index, and cup size were found in positive correlation with each other. Body mass index was negatively correlated with forced expiratory volume in 1 second, forced vital capacity, and forced expiratory volume in 1 second / forced vital capacity. Conclusion: Breast size had no correlation with lung function in healthy volunteer women. Body mass index seems as the main factor affecting the lung function.