A substantial part of Europe consists of suburban landscapes. The factors determining the species diversity and composition in these seemingly uninteresting areas are, however, underexplored. We studied the factors determining the species diversity and composition of plant communities in a suburban postindustrial landscape in the central part of the Czech Republic. We recorded 242 phytosociological relevés (5m×5m) in a regular grid over an area of 2.5km×1.8km. Data on abiotic factors (slope, solar irradiation, bedrock) and landscape structure (distance from relevé to the nearest road, settlement and habitat edge) were obtained from digital maps. Patterns of plant species traits were also examined. A total of 387 species of vascular plants was recorded, and a majority of the species (58%) was found in five or fewer sites. The species abundances in the region were significantly affected by several traits. A long vegetation gradient including woodlands, shrubs, grasslands and ruderal and weedy communities were observed in the suburban landscape. Land cover was a crucial determinant of both the diversity and species composition. The number of species and evenness was significantly influenced by different abiotic and landscape structure factors. The species composition was affected by all of the tested factors. We found relationships between species traits and landscape structure characteristics. The results of this study showed that the species richness and the diversity of vegetation types are relatively high in suburban landscapes and are mostly determined by human activities forming the landscape structure.