It has an area of 10.66 km² and a population of 46,410 (as of 2001) giving a population density of 4,352.8 inhabitants per km². Local landmarks include the Parque das Nações, the Palácio do Contador-Mor, a pedagogic farm, Casa da Fonte do Anjo, Quinta da Bica, Quinta da Fonte do Anjo, Capela da Quinta da Fonte do Anjo.
The parish was created in 1397, probably resulting in the division of a part of Beato (to the south) and Sacavém (to the north). Between 1852 and 1886 Santa Maria dos Olivais formed a large municipality, predominantly rural, including 22 civil parishes.
In 1864 it occupied a surface of approximately 223 km² and had a population of 25,495, and of 29,491, in 1878.