BACKGROUND: According to Korean regulations, bottled waters (BWs) can not be treated with chemical disinfectants like chlorine, so UV and ozone disinfection is applied. During the past several years, chemicals were detected in some BWs, and the public was concerned about the safety of BWs. METHODS AND RESULTS: Mineral waters were stored for 180 days at 25℃ and 50℃, tested acetaldehyde and formaldehyde by HPLC. When mineral waters were put in a PET bottles, the formaldehyde level ranged from 5 to 66 μg/L during 180 days at 50℃. While the acetaldehyde level ranged from 31 to 221 μg/L, it was low than 16 μg/L in glass bottle. CONCLUSION(s): This result showed that formaldehyde and acetaldehyde were detected higher in PET bottles than glass bottles, these also increased depending on the time of storage. Concentration of formaldehyde and acetaldehyde could be significantly influenced by the time of storage and temperature.