Possums are marsupials of the Family Phalangeridae. Two species of possums are encountered by pest controllers as temporary pests of houses:

Ringtail possum (Pseudocheirus peregrinus): This has a short head, pointed muuzzle, short round ears and a tapered tail, the terminal three-quarters of which is pale. It occurs along coastal Australia from Queensland to South Australia.

Brushtail possum (Trichosurus vulpecula): This possum is often encountered where there are trees. It feeds naturally on buds, fruits of trees and shrubs, but also like to feed on bread, cake and fruit. It occurs from northern Queensland to South Australia and is the possum most frequently encountered.

Possums live naturally in cavities of trees. They shelter there during the day and emerge to feed and explore at night. Possums enter roof voids when their natural nesting sites have been removed, mainly through broken tiles, damaged eaves and displaced ridge capping. When in the roof they make noises at night, urinate and defecate on ceiling plaster, causing stains and odours. Chimneys are also favoured sheltering places.