I'm terrible with introductions when critiquing, so here goes. The stance is funny and makes me think that he should be dancing in an M.C. Hammer video and sporting parachute pants. His feet and fists look small compared to his bulky limbs, and his left arm looks somewhat short. Maybe it's the angle you tried to draw it at, but without shading, it's hard to tell what you were trying to do with that arm. Why is he pointing downward with his right arm with a trail of smoke?
He is ridiculously thin, especially when you take into account that if you combined both the arms you drew, they're bigger and thicker than his chest and stomach. The mask looks awkwardly designed as well, the triangle patterns don't match on both sides, and the mask looks unusually long on his left side.
The colour is... Well, it's hard to comment on colours for a character known for sporting only gray and black, but you used too much black over the gray here, so it kind of looks like his trademark gray's a bit of an afterthought. Makes me think of Ermac with his new designs that don't feature as much red as they used to, except that since Smoke's gray, it's harder for the gray to stand out and looks somewhat faint.
It's definitely not a bad picture, and you've said that you did this a while ago, but I do think it can be fixed and improved. 3/5 from me.

Thanks for the constructive criticism. I'll try to take your advice into account the next time I'll draw. In fact this drawing is a bit over four years old albeit it's new to the public. I can draw and design better now but when I have a lot unfinished pieces of art, this remains the piece of art with the most effort I've put into so far. I've noticed the big flaws in its anatomy too and I also noticed afterwards that there are suddenly four gray lines under the belt in his Y-garment. I'll submit more of my artwork, whilst they might not be as good as what I've submitted earlier, while now creating entirely new pieces of art. So more to come.

"My, my, my smokeycut hits so hard
Makes you scream 'Oh, my Lord'
And you regret catching me
In the Hidden Forest behind that tree..."

lol yeah the finger pointing down is funny..i think if he was pointing at you..
it is a nice piece of art..i want smoke to be silver though not grey, i hope they make him silver

I have a different kind of Human Smoke in mind today, just maybe I will draw it someday. Yeah, Smoke is the silver ninja opposed to Scorpion the gold ninja.