Whoa! What's good girl Kylie Jenner doing smoking an electronic cigarette, puffing away on camera in this new Snapchat video?! We thought the 18-year-old had a better head on her shoulders!

More important -- what's she smoking? We're pretty sure the teen doesn't do tobacco ... so it is ... something else? I mean, we didn't see her break out the Visine. But she sure has some experience blowing smoke rings!

Regardless of what she's smoking, is Kylie sending the wrong message to her fans? Whether it's tobacco, cannabis, or flavored e-liquid -- none of it's great for your health and vape pens can certainly be a gateway device. Maybe she's getting paid by a vape company? That's our guess!