The aim of this paper to summarize vascular plant diversity of the Istanbul province (Turkey). The province covers just 5110 km(2), yet support remarkably high diversity of plant richness with approximately 2500 flowering plant taxa more than total flora of the Netherlands or United Kingdom. The wide diversity of unusual habitats has allowed the development of an astonishingly rich flora. Grassland, forests, heathlands, sand dunes and other coastal habitats and wetlands within the province are high international importance to native conservation. Much of the province of Istanbul is of importance to nature conservation, but 7 areas stand out as being exceptional called Important Plant Areas: 1. Agildere & Agacli dunes; 2. Terkos - Kasatura forests and coastline; 3. Gumusdere-Kilyos dunes; 4. Hadimkoy-Kemerburgaz Grassland and Heatlands; 5. Upper Bosphorus: 6. Sahilkoy to Sile dunes & forests; 7. Istanbul's Asian Hills, Omerli Basin. The most of herbarium specimens of the vascular flora of Istanbul have been deposited in ISTE Herbarium. Because of the this paper presented in the Apiales Meeting, the first Apiaceae specimens kept in ISTE, Artedia squamata L. and two rare Apiaceae species (Peucedenum obtusifolium and Heptaptera triquetra) have been discussed.