Paris Hilton -- Can't Handle a Foot-Long

Paris Hilton is not so cool that she can't chow down on Subway ... she just thinks she's too cool to be SEEN with a Subway sandwich.

Everyone's favorite leggy socialite was spotted Monday hitting up the popular sandwich shop in New York City, but as soon as she walked out ... and realized the paps had seen her ... she tried (unsuccessfully) to slip the sub behind her clutch.

Either she wants to promote fashion over food, or she is still holding on to her Carl's Jr. days. It's gotta be the latter ... for us.