After an exodus of young talent through the Gillette AFL Trade Period, securing Polkinghorne was significant for the Lions as the club looks to build under a new coach.
Both Polkinghorne and Maguire signed one-year extensions for next season.
"It’s probably no secret that James spent some time over the off-season weighing up his AFL future, but after speaking with new senior coach Justin Leppitsch, he decided to remain in Brisbane," general manager of football operations Dean Warren said.
"The club sees him as being a valuable player who is about to enter the prime of his career.
"Matt, on the other hand, is about to reach the twilight of his career, but his performances over the past few years have shown that he can still match it with some of the best forwards in the competition.
"He was particularly important last year when Daniel Merrett was moved forward, and is another experienced campaigner that our young defenders such as Justin Clarke and Jordon Bourke can learn from."
Polkinghorne, 24, has played 92 games in six seasons with the Lions since being recruited with pick No.41 at the 2007 NAB AFL Draft.?
Maguire has played 155 games, joining the Lions after 99 games with St Kilda.
The Lions re-signed young defender Clarke earlier this month but the club has struggled to retain players from interstate.
Elliot Yeo (West Coast), Sam Docherty (Carlton), Jared Polec (Port Adelaide), Billy Longer (St Kilda) and Pat Karnezis (Collingwood) all returned to their home states during the trade period.
Meanwhile, Jesse O’Brien has been told he will not be offered a new contract after 17 games in four seasons.
Originally recruited from North Adelaide with pick No.73 in the 2009 NAB AFL Draft, the injury-plagued 22-year-old suffered a persistent groin complaint in 2013 but pushed into the team in round 19.
"Following the Trade Period, it became apparent that we would need to find another spot on our list so that we could potentially use our six selections inside the second round of the upcoming Draft,” Warren said.
"Unfortunately Jesse was a casualty of the list management process, however we wish him all the best with his future football career and thank him for his contribution."
