To advance our restricted knowledge on mosquito biodiversity and distribution inBelgium, a national inventory started in 2007 (MODIRISK) based on a randomselection of 936 collection points in three main environmental types: urban,rural and natural areas. Additionally, 64 sites were selected because of therisk of importing a vector or pathogen in these sites. Each site was sampledonce between May and October 2007 and once in 2008 using Mosquito Magnet LibertyPlus traps. Diversity in pre-defined habitat types was calculated using threeindices. The association between species and environmental types was assessedusing a correspondence analysis. Twenty-three mosquito species belonging totraditionally recognized genera were found, including 21 indigenous and twoexotic species. Highest species diversity (Simpson 0.765) and species richness(20 species) was observed in natural areas, although urban sites scored alsowell (Simpson 0.476, 16 species). Four clusters could be distinguished based onthe correspondence analysis. The first one is related to human modifiedlandscapes (such as urban, rural and industrial sites). A second is composed ofspecies not associated with a specific habitat type, including the now widelydistributed Anopheles plumbeus. A third group includes speciescommonly found in restored natural or bird migration areas, and a fourth clusteris composed of forest species. Outcomes of this study demonstrate theeffectiveness of the designed sampling scheme and support the choice of the traptype. Obtained results of this first country-wide inventory of the Culicidae inBelgium may serve as a basis for risk assessment of emerging mosquito-bornediseases.