
En el 2007, firmó un contrato como solista con Capitol Records y en 2008 lanzó su álbum One of the boys, el cual debutó en la posición número nueve en el Billboard 200 y en la posición diecinueve del United World Chart. El 20 de noviembre lanza su primer sencillo titulado "Ur So Gay", el cual causó mucha controversia por su letra. En el mes de diciembre del 2007 atrajo la atención cuando Madonna declaró en dos programas de radio estadounidenses que "Ur So Gay" era su canción preferida del momento. En mayo lanzó su segundo sencillo, "Thinking of You", como promoción solamente. Ese mismo mes lanza su tercer sencillo, "I Kissed a Girl", que pronto se convirtió en un éxito mundial alcanzando la posición número uno del Billboard Hot 100. También fue la canción número mil en hacerlo. Su cuarto sencillo, "Hot N Cold" fue lanzado en las radios americanas el 9 de septiembre y ha alcanzado un gran éxito a nivel internacional al igual que su anterior sencillo. Hé aqui su sencillo Hot n' cold.
You change your mind
Like a girl changes clothes
Yeah you, PMS
Like a bitch
I would know
And you over think
Always speak
Crypticly
I should know
That you're no good for me
[CHORUS]
Cause you're hot then you're cold
You're yes then you're no
You're in then you're out
You're up then you're down
You're wrong when it's right
It's black and it's white
We fight, we break up
We kiss, we make up
(you) You don't really want to stay, no
(but you) But you don't really want to go-o
You're hot then you're cold
You're yes then you're no
You're in and you're out
You're up and you're down
We used to be
Just like twins
So in sync
The same energy
Now's a dead battery
Used to laugh bout nothing
Now your plain boring
I should know that
You're not gonna change
[CHORUS]
Cause you're hot then you're cold
You're yes then you're no
You're in then you're out
You're up then you're down
You're wrong when it's right
It's black and it's white
We fight, we break up
We kiss, we make up
(you) You don't really want to stay, no
(but you) But you don't really want to go-o
You're hot then you're cold
You're yes then you're no
You're in and you're out
You're up and you're down
Someone call the doctor
Got a case of a love bi-polar
Stuck on a roller coaster
Can't get off this ride
You change your mind
Like a girl changes clothes
[CHORUS]
Cause you're hot then you're cold
You're yes then you're no
You're in then you're out
You're up then you're down
You're wrong when it's right
It's black and it's white
We fight, we break up
We kiss, we make up
(you) You don't really want to stay, no
(but you) But you don't really want to go-o
You're hot then you're cold
You're yes then you're no
You're in and you're out
You're up and you're down,down,down,down...