Question : Problem: Can I add mp3 to an already burned CD using iTunes?

Is it possible in Itunes, upon creating a playlist and burning as mp3CD, to add songs to the CD after it has been burned?

I remember in the past it was possible to leave a data cd open for further burning.

Answer : Problem: Can I add mp3 to an already burned CD using iTunes?

You won't be able to do it from within iTunes. It writes single session CDs in fact I'm pretty sure it closes the session too for Music & MP3 CDs.

You could use the Disk Utility application to see the status of your CD.

Multisession CDs can be written with something like Roxio Toast or Disco