A forest inventory was carried out in 12 forest islands scattered in the large savanna matrix of Roraima, northern Brazilian Amazon. The fieldwork occurred between 2013-2014 based on direct observations along transects established between the edge-interior gradient of each sampled forest island. It was investigated species composition and forest structure variables: stem diameter (DBH = diameter at breast height ≥ 10 cm) and total height (visually estimated). All floristic dataset was correlated with the forest fragment size. The survey was conducted by the Research Group Ecology and Natural Resource Management of Roraima Savanna, associated to the National Institute for Research in Amazonia (INPA).