ZenithOptimedia, Ikon and Maxus are thought to be in the running for iSelect's $15 million media account with three other agencies also thought to be on the shortlist.
Incumbent M2M and iSelect parted ways earlier this year, with the incumbent choosing not to be part of the pitch process.
None of the agenices would confirm their involvement in the pitch.
According to Nielsen figures, iSelect spent $15 million on main media last year as the online comparison site sought to ramp up its business.
In announcing the review, iSelect said it was looking to review its current hybrid internal/external buying plan, but said it may be open to "fresh ideas".
"A hybrid internal and external media solution seems to make the most sense for us," iSelect's marketing director Geraldine Davys said at the time.
UPDATE: Bohemia and Slingshot Media are also thought to be in the running.
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