The possibility that broad leaf trees can be reservoirs for phytoseiid mites was investigated by determining their occurrence and species diversity on common deciduous tree species. No phytoseiid mites were found on Betula pendula and Populus tremula. Altogether 280 specimens of phytoseiids belonging to six species (Neoseiulella ace-ri, N. tiliarum, Paraseiulus soleiger, Euseius finlandicus, Phytoseius severus, Typhlodromus rhenanus) were found on Acer platanoides, Fagus sylvatica, Quercus robur and Salix caprea. Ph. severus was the dominant phytoseiid species on S. caprea, while N. aceri was most abundant on A. platanoides. The greatest abundance and species diversity of phytoseiids were found on S. caprea that can thus constitute an excellent reservoir for some phytoseiid mites, particularly Phytoseius spp.