<p>The senescence and preservation mechanisms of ethylene-sensitive and ethylene-insensitive cut flowers are different. Hydrogen peroxide (H₂O₂), an important signal molecule for plant development, has been proved to improve the vase life of cut flowers. In order to clarify the preservative role of H₂O₂ in cut flowers with different ethylene sensitivity, cut lily ‘Sorbonne’ (ethylene-insensitive) and cut rose ‘Diana’ (ethylene-sensitive) were treated with exogenous H₂O₂. The 1-aminocyclopropane-1-carboxylic acid (ACC) content and reactive oxygen species (ROS) metabolism were observed in the study. The results showed that the endogenous H₂O₂ decreased during the vase life in cut lily, while increased in cut rose. The level of superoxide anion (O₂^˙ˉ) and malondialdehyde (MDA) increased in both flowers. The superoxide dismutase (SOD), catalase (CAT) activity and the ascorbic acid (AsA) content decreased, the peroxidase (POD) activity increased with the senescence of two flowers. The exogenous H₂O₂ enhanced SOD and CAT activity, increased AsA content, and inhibited the production of ROS in both flowers. The peroxidation damage of both flowers was reduced by H₂O₂ treatment. The ACC content was inhibited by the exogenous H₂O₂ in rose, while it was increased in lily. These results have shown that the effects of exogenous H₂O₂ on delaying the senescence and alleviating the peroxidation damage were associated with the endogenous ethylene and antioxidant defense ability in cut rose. The same effects were mainly related to the antioxidant defense system rather than ethylene metabolism in cut lily. The application of H₂O₂ to improve the ornamental value in rose and lily cut flowers provides a convenient and fast way of preservation.</p>