Skuas are similar as well but are bulkier, thicker-necked, with much more prominent wing patches.
Jaegers look most similar to each other.
Adult Pomarines can be safely identified by either their long, spoon-shaped central tail feathers or their mottled breast band. The light phase has a heavier breast band than the Parasitic Jaeger. Juvenile jaegers are very difficult to tell apart but the tail feather shape is still diagnostic though subtle and the uppertail covert pattern is useful as well. Long-tailed Jaeger is very small and dainty and should rarely be confused with Pomarine.