This study is the first direct comparison of the diversity of phytophagous insects associated with a parasitic plant and its host plants. Specifically, we compared the species composition, density and host specificity of psylloids or jumping plant lice (Hemiptera: Psylloidea), inhabiting hemiparasitic box mistletoe Amyema miquelii, and three of its host Eucalyptus species: Eucalyptus blakelyi, Eucalyptus melliodora and Eucalyptus polyanthemos. Insects were sampled by restricted canopy fogging in remnant Eucalyptus woodlands in an agricultural region of temperate south-eastern Australia. Although most psylloids are understood to be mono- or oligophagous, most species in our survey were found on the foliage of both mistletoes and eucalypts. Nevertheless, analysis of density patterns and reference to previous work on psylloids supports the high degree of host specificity for psylloids, leading to distinct assemblages on these two intimately associated plants. We show that (1) there were two mistletoe-associated species of psylloid and 18 eucalypt-associated species; (2) there were a large number of tourist species, as indicated by known psylloid/plant host associations; and (3) psylloid density was higher on eucalypt than mistletoe leaves. The different psylloid assemblages found on box mistletoes compared with their host plants are likely to be due to differences in the foliar properties implicated in host specificity and host selection by phytophagous insects. Further research is required to understand the ecological dynamics and evolutionary origins of these arboreal assemblages.