Korean wetlands suffer from various human activities. Currently, few natural inland wetlands are left in the Korean peninsula, but most of them have been influenced by development of reservoirs, dams, and rice fields. Biodiversity of wetland insects surveyed from typical Korean inland wetlands, including estuary wetlands, riverside wetlands, back marshes, mountain wetlands, and lowland artificial wetlands (rice fields), are presented in this study. Particular attention is given to two flagship species of wetland insects, the giant water bug (Lethocerus deyrollei) and Nannophya pygmaea (Libellulidae, Odonata), in terms of conservation. These two species are listed as endangered wildlife species and being protected by the Ministry of Environment of Korea.  The giant water bug is mainly distributed in lowland wetlands, such as ponds, pools, and irrigational channels of rice fields, but the population has drastically decreased for last a few decades in Korean peninsula. Our field and laboratory studies demonstrate that their light attracting behavior as well as habitat and water quality degradations caused a local extinction of the population. On the other hand, the local population of N. pygmaea has increased recently due to an increase of abandoned rice fields caused by the decrease of agricultural population in rural areas.