Studies have shown that the Caatinga has two vegetation types related to different soils originated from crystalline and sedimentary. However, it is unclear whether the flora as a whole varies in relation to this difference or if it only varies for certain plant habits. This article provides a comparative analysis of the different habits of flowering plant species that occur on different soil types in a semi-arid region of northeastern Brazil. Sixty plots (10 x 10m) were established to collect woody species and 300 plots (1 x 1m) were established to collect herbaceous species. The plots were in soils of crystalline and sedimentary origin, and drainage and relief were taken into consideration. One hundred and fifty species distributed in 40 families were recorded. Species richness was greatest in Leguminosae (37 spp.), Euphorbiaceae (16 spp.) and Convolvulaceae (13 spp.). There were 101 woody species and 49 herbaceous species, suggesting that the woody habit responds better to local morpho-pedological differences.