Wetlands contain both aquatic and terrestrial environments which generates high biodiversity. However, they are commonly associated with mosquitoes (Diptera: Culicidae), and mosquitoes are usually regarded as negative by humans because they can cause nuisance and transmit diseases. This thesis aimed to clarify the association between mosquitoes and wetlands and to achieve a more balanced view of biodiversity in wetlands by including mosquito diversity. Studies on adult mosquito diversity and assemblages were performed in 18 wetlands spread over Sweden. The Swedish mosquito species were organized in ten functional groups based on four life-history characteristics. This classification was used as an additional diversity measurement and as a tool for presentation of mosquito data. Mosquito diversity showed several of the well-established diversity patterns such as a latitudinal gradient, a species-area relationship and a distribution-abundance relationship. In a landscape perspective, diversity of both mosquitoes and dytiscids (Coleoptera: Dytiscidae) were positively influenced by a high proportion of permanent water and a high amount of open areas, indicating co-varying diversity patterns. Mosquito assemblages in the Nedre Dalälven region were mainly structured by the extent of flooded areas and wetland type (wet meadow, swamp and bog). In addition to the influence of the proportion of temporary wetlands at a local scale, the proportion of forest gained importance at larger spatial scales and in relation to dispersal distances of species. In southern Sweden, mosquito faunas differed between natural and constructed wetlands, partly reflecting differences in wetland size. In an experiment, different responses of two co-occurring mosquito species to rapid larval habitat desiccation indicate that weather conditions after a flood could influence mosquito assemblages. The conclusions of this thesis provide suggestions on how to construct and position wetlands for increased insect diversity, and indicate that low abundance of major nuisance species might be crucial for acceptance of wetlands near human settlements.