CBDs are all over the plant
The entire weed plant, aside from the inside of the stems and the roots, does contain certain CBD.
This is due to the fact that the resin glands are all over the plant. Some parts, such as the fan-leaves, only produce/contain trace amounts of the desired CBD and THC CBD. Even though the mentioned glands are also present in this kind of leaves.
There are different types of leaves on the weed plant. Everyone who took a closer look at a hemp bud should have already noticed that they consist of a big portion of trichome sparkled leaves. The leaves surrounding the buds, however, are not to be put in the same category as the big fan-leaves when it comes to the contained THC and CBD amounts.
Theoretically, it is possible to smoke nearly anything. If you can set fire to it, you can probably smoke it! And as soon as anything else than oxygen enters your lungs, you may very well feel a buzzing effect.
But getting a buzz from smoking whatever burns usually is not due to possible CBD-contents and in general, can be risky. Ever heard of Carbon-Monoxide-Poisoning?
Another thing to keep in mind is that weed leaves might have been treated with unknown fertilizers so you could be in for a completely unknown and totally risky ride. So if you are not sure how the plant has been grown, you might want to avoid it in general.