JENNIFER ANISTON’s addicted again – and I DON’T mean JOHN MAYER!

After kicking a years-long cigarette habit in late 2007 with a hypnotherapist’s help, insiders say Aniston’s hooked on Marlboro Lights again – and it happened right after her hookup with Mayer.

Now Our Friend’s furious with herself, freaking because she’s sneaking smokes like a naughty teenager and desperately ducking foe-togs to avoid her biggest fear – getting busted with a butt by nicotine-phobic BFF COURTENEY COX!

Aniston told pals there’s an upside to smoking for her: It calms her nerves, kills her appetite and keeps her smokin’ bod bikini-teeny – but she admits she’s depressed about backsliding after a brief win against the habit that’s gripped her for years.

Burning Question: Is it monkey-see-monkey-do? An obscure Internet report says Jen was spotted sneaking a puff of loverboy Mayer’s cig while they were out on the town.

Hey, Mr. Enabler…are those smokin’-hot kisses fun?