Landscape metrics are widely used to investigate the spatial structure of landscapes. Numerous metrics are currently available, yet only little empirical research has comparatively examined their indicator value for species richness for several taxa at several scales. Taking a Mediterranean forest landscape - Dadia National Park (Greece) - as a case study area, we explored the performance of 52 landscape level landscape metrics as indicators of species richness for six taxa (woody plants, orchids, orthopterans, amphibians, reptiles, and small terrestrial birds) and for overall species richness. We computed the landscape metrics for circular areas of five different extents around each of 30 sampling plots. We applied linear mixed models to evaluate significant relations between metrics and species richness and to assess the effects of the extent of the considered landscape on the performance of the metrics. Our results showed that landscape metrics were good indicators for overall species richness, woody plants, orthopterans and reptiles. Metrics quantifying patch shape, proximity, texture and landscape diversity resulted often in well-fitted models, while those describing patch area, similarity and edge contrast rarely contributed to significant models. Spatial scale affected the performance of the metrics, since woody plants, orthopterans and small terrestrial birds were usually better predicted at smaller extents of surrounding landscape, and reptiles frequently at larger ones. The revealed pattern of relations and performances will be useful to understand landscape structure as a driver and indicator of biodiversity, and to improve forest and landscape management decisions in Mediterranean and other forest mosaics.