A study was conducted to determine whether hyperbaric treatment has an effect on the shelf life of lettuce during short-term storage. Lettuce was treated with different pressure and temperature conditions (100–850 kPa at 20 °C and 100 kPa at 4 °C). A preliminary experiment was performed with different treatment periods, that is, 3, 5 and 7 days. Hyperbaric treatment of lettuces at 20 °C caused noticeable changes in sensory quality, but the product was still marketable after 3 days. On the other hand, the cold-stored lettuce showed little degradation even after 7 days of treatment, at which time all the lettuce treated at 20 °C was unmarketable. At 5 days of treatment, the respiration rate of hyperbaric-treated lettuces at 625 and 850 kPa remained fairly stable, while that of the lower-pressure-treated lettuce began to increase, indicating the initiation of decay. The 850-kPa hyperbaric treatment showed better quality results than the 100 kPa, 20 °C treatment. Overall, hyperbaric treatment has the potential of being used as an alternative technique for short-term storage of lettuce without refrigeration.