The digestive tracts of preserved specimens of six species of New Guinean pseudocheirid (ringtail) possums (body mass 148.1250 g) and four species of New Guinean phalangerids (cuscuses) (7302400 g) were compared. A preliminary study on Australian common ringtail possums (Pseudocheirus peregrinus) suggested that, within certain limits, data from preserved material were applicable to fresh specimens. The New Guinean ringtails were primarily folivorous, but the diet of the two smallest species contained more non.leaf material and was of higher quality, on the basis of higher (P<0.05) nitrogen levels in their gastric contents. Like P. peregrinus, New Guinean ringtail possums selectively retain fine feed particles and bacteria in their caecum, and may also be caecotrophic. The New Guinean phalangerids are less specialised in their diets, taking a wide range of leaves, bark and fruits. There was no evidence for caecotrophy or selective retention of bacteria in their caecum, but there was evidence for selective retention of fine feed particles. In the latter characteristic they differ from the Australian phalangerid Trichosurus vulpecula (the common brushtail possum).