Red lionfish were transported outside their native Pacific range to supply aquaria, subsequently escaped or were released, and have established breeding populations in Atlantic reefs. This invasion has negatively affected coral reef fishes, reducing recruitment success through predation. To provide insight into the factors explaining invasion success, we examined the distribution and abundance of native lionfish in 2 regions of the Western Pacific (Marianas and Philippines). Densities of lionfish and other predatory coral reef fishes were evaluated via stratified surveys targeting habitat preferred by lionfish. There were considerable regional differences in species composition of lionfishes in general and density of Pterois volitans in particular. Red lionfish were uncommon on Guam (3.5 fish ha-1) but 6 times more abundant in the Philippines (21.9 fish ha-1). Densities in both regions were an order of magnitude less than reported in the invaded Atlantic. There was no relationship between density of lionfish and that of other reef predators, including groupers. Both native populations of P. volitans were more common on reefassociated habitats (sandy slopes, reef channels, and artificial reefs) than on coral reefs. On Guam, P. volitans was more abundant in areas of low water visibility (reef channels and river mouths) compared to reefs with high water clarity. Lionfish in their native range are habitat generalists that occupy various environments, including areas with low salinity and high sediment loads. This plasticity in habitat use helps explain invasive success, given that ecological generalization is recognized as a major factor accounting for the successful establishment of invasive species. © Inter-Research 2014.