While iTunes doesn't support FLAC files, it's very easy to convert them to Apple Lossless, or ALAC, an equivalent lossless format that iTunes supports. ... (The same is true with other uncompressed or lossless formats, such as WAV, AIFF, APE, SHN, and others.)

Does iTunes automatically convert FLAC?

On a Mac you could use the free XLD tool - which can convert from FLAC to various other formats including Apple Lossless. XLD can also do this and automatically add the results directly in to iTunes.

Does iTunes convert FLAC MP3?

You can convert the flac files to wav using the standard flac tools. iTunes will import wav files, and you can convert them to mp3 or AAC there.