The 22-year-old is said to be on the Yorkshire club's respective radars.
The Peterborough Telegraph is reporting that the Yorkshire clubs have both been keeping an eye on the player in recent weeks, although there is no mention of any imminent bid for the player.
The Posh however will be worried, with Connor Washington recently moving to QPR fans might fear a mini-exodus.
Sheffield Wednesday would no doubt have the cash to bring him in. They are all set to pay big money for Gary Hooper and are chasing Jordan Rhodes as well - so financially they would be able to offer Peterborough a good fee.
Leeds meanwhile have recently cashed in. Sam Byram left the club to join West Ham United yesterday.
But both Wednesday and Leeds would need to stump up the right amount if they do decide to act on their apparent interest.
Peterborough chairman Darragh MacAnthony will not want to lose Maddison unless the club are adequately compensated.
Maddison is a former youth product at Newcastle United. He came to Peterborough from non-league Gateshead in 2014 and the attacking midfielder has gone on to establish himself at London Road.