US rapper The Game had been scheduled to play on the NME/Radio 1 stage in the afternoon at the Scottish bash, while 80s-style popster Ladyhawke was set to headline the Red Bull Bedroom Jam Futures Tent.
Dally King had been set to play on the BBC Introducing stage.
Festival organisers have not given reasons for the cancellations yet.
Blur, Pete Doherty, Lily Allen and Doves are among the acts set to play T In The Park later today – the final day of musical action at the event.
Plus, make sure you get next week’s issue of NME, on UK newsstands from July 15, for the ultimate T In The Park 2009 review.