Yes it does.
The front of a tank is the most armoured, and therefore will take the least damage.
The sides are less armoured than the front, and will take less damage than the back.
The back is lightly armoured, and will take a fair amount of damage.
The top is extremely lightly armoured, and will take a lot of damage. In fact, in my recent testing, you can take out an enemy tank in two shots if you can hit the top of the tank (which is possible in close range by aiming for the rotating part of the tank).
The bottom has no armour and will take the most amount of damage possible (except you won't really hit the bottom much except with mines and c4).
Your best bet is to hit the top, and if that's not possible, the back.
On the other hand, if you're in a tank, always position your front to where you think the threat is coming from.
For much more detail, see the detailed experiments at
Tanks have armor that protects their front and affects damage done by a majority of the anti-tank weaponry. If you can, aim for the rear of the tank. If the weapon is question is affected by armor, you'll do about 3 times as much damage if you hit the rear, and about 1.5 times as much damage if you hit the side. If you can, avoid hitting the front of the tank with your shots at all costs.