Demi Lovato has heaped praise on Adam Lambert's Glee debut.

The singer made his first appearance on the show alongside the X Factor USA judge last night (November 7) in the US.

The episode, which is entitled 'A Katy or a Gaga', sees Lambert play the role of Eliott 'Starchild' Gilbert and he received rave reviews for his part.

Speaking to Perez Hilton prior to the episode's airing, Lovato said:

"He's great. He's a really cool guy. He's super talented."

She added: "You can just see his talent in this episode for sure".

As previously reported, Glee star Darren Criss said of Lambert's performance on Twitter:

"And of course BIG congrats to my friend @adamlambert for CRUSHING his debut on #glee. The world never ceases to be impressed by your talent!"

Lambert could be seen singing songs such as Lady Gaga's 'Marry The Night' and Katy Perry's 'Roar' on the show.