Mätäoja is between two city districts, the densely built Myyrmäki and Kaivoksela. The riverbed of Mätäoja winds through a flood meadow with thick willow bushes. Sometimes, the little brook flows in its groove, but at other times the clear brook disappears and the flood meadow turns into a network of hummocks and smaller brook grooves. Two ponds have been dug out under the bridges crossing the brook. Small open water ponds are here and there all along the conservation area. A small open swamp is …found in the northern part of the area. The Mätäoja valley has some rare plants and animals. All in all, Mätäoja is one of the greatest and most valuable natural sites in Vantaa.
Louhela black alder swamp has been separated from the Mätäoja nature conservation area. The solid black alder trees protect the thick marsh calla vegetation. In many places, bittersweet nightshade vines, which may grow several metres long, twine around the willow branches on the riverbanks of Mätäoja. Bittersweet nightshade belongs to the same genus as the more familiar potato.
Mätäoja valley is also a home to white adder's mouth, an orchid species under special protection. Other plants in the area include the yellow iris with its impressive bloom, thick growths of water horsetail, and great water dock, which is very rare in Vantaa.
The most visible and audible animals of Mätäoja are its birds. Thrush nightingales, garden warblers, Eurasian blackcaps and many other birds sing in the thick crops of trees in spring. Thanks to the ponds dug along the brook, water fowls come to nest in the area, such as mallards, goldeneyes and Eurasian teals. The thickets along Mätäoja also offer shelter for larger animals, such as moose and roe deer.
The most famous inhabitant of Mätäoja, hylochares cruentatus, a species of false click beetle, hides most of its life as a larva on the trunks of the bay willows and dark-leaved willows growing along the brook. At the moment, this species has only ever been discovered in two places in the whole world. The other place, the willow flood meadow of Pikkujärvi, is also in Vantaa.
The habitat of the white adder's mouth, an orchid species under special protection, was protected in Mätäoja valley in 2004. After this, the Louhela black alder swamp was protected as a nature type in 2007. In 2012, the habitat of hylochares cruentatus, also under special protection, was protected. In total, the size of the protected area in Mätäoja valley is now 29.8 hectares.