Well, smoking is one of the worst things you can do for your health and your skin. Smoke actually constricts blood vessels to the skin, and it can cause your skin to thin over time. This will lead to increased fine lines especially around the mouth, deep edged lines especially around the cheek, and also a discoloration, almost a yellowish appearance to the skin.
Some people report that smoking can actually add nine years to your skin appearance, but quitting smoking can actually start to reverse those changes. So it's never too soon to quit and please don't start if you haven't started.