Urban and suburban parks can play an important role in the conservation of biodiversity, especially in a strongly urbanised region like Flanders (Belgium). A previously developed method for monitoring biodiversity was applied to 15 parks in Flanders. This method took both habitat and species diversity into account and resulted in 13 biodiversity indicators. The results show that urban and suburban parks can have a high species richness, especially if they consist of different more or less semi-natural habitats. The relationships between the biodiversity indicators and the ecological factors affecting the biodiversity were examined using multivariate analyses and correlation techniques. Park area was the main factor explaining the variation in biodiversity indicators, so larger parks could contribute more to the conservation of biodiversity than small ones. A biodiversity score based on habitat diversity and species richness was proposed to summarise and evaluate the biodiversity. This score is not correlated with the park area and is therefore considered as a reliable indicator for comparing biodiversity in parks of different area.