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Probably not, since they are nothing but empty husks. But it's difficult to know whether that's possible or not since we don't really have any in-game evidence, at least, as far as I know.  Timelinesplitter Chaos 14:54, November 25, 2012 (UTC)

I don't know if this counts as evidence, but in 358/2 Days, if you look at Roxas, he's always moving up and down, as if he's breathing. Also, Axel and Roxas are nobodies, and they eat sea-salt ice cream all the time. ~DarmaniTheFourth
^ True that they can breathe and eat, but they likely do not need to breathe and eat.  Timelinesplitter Chaos 23:46, November 25, 2012 (UTC)