Portugal with its Mediterranean climate has frequently wildfires during summertime. The knowledge of the composition and the configuration of patches that constitute the forest matrix (Godinho-Ferreira et al., in press) is important to understand the processes occurring in it, including forest wildfire probability. Forests vertical structure depicted from the third revision of the Portuguese National Forest Inventory (NFI) show different layers composed by different kinds of species occupying different percentage of cover, identifying 10 main forest types and 22 structural types (GodinhoFerreira et al., 2005). A first analysis of NFI sampling plots burned between 1999 and 2005 indicates that large and very large patches of maritime pine and eucalyptus forests have the highest rates of burning areas. This presentation is part of a first and coarse approach aiming to develop more accurate methodologies within the project "PHOENIX – Forest conversion in burned areas" (POCI/AGR/58896/2004), particularly “Task 1 – What forest types are less likely to burn?”.