New Kitten and family dog

Just got a new 4 month old kitten for xmas and we seem to have a problem between the new kitten and our existing dog. The kitten attacks the dog whenever around him. What do I do? Also, whenever we go into the room to approach him he hisses and then he seems to be alright when being petted, the purring starts and he will fall asleep in your lap. Any suggestions, I really don't want to return this cat to the shelter, he is really cute
Thanks

It might just be overstimulation. If you JUST got him, I'd say confine him to one room with all his necessities for the first little bit, let him get used to that room and the sounds/smells of the house. The dog and him can smell eachother through the door. Then, slowly introduce them for short periods of time and make sure the kitten has somewhere to go that is out of reach. He may be feeling cornered by the dog. Chances are he's just on edge because the environment is so new. I'm sure if you give it some time, he'll relax a bit. Good luck!

It's way too early to give up on the kitten.
The above advice is great. The kitten is probably scared and trying to get her bluff in on the dog. My kitten is the boss of three HUGE dogs and she used to do the same thing.
We also have out kitten's stuff in out guest room, with a child gate across the door. We keep the bottom of the gate up off the floor about 4 inches, just low enough that the dogs can't get in.

They are not 'natural' friends to say the least, and while they might become friends, it will take time. I do suggest you be around while it's happening as you wouldn't want anything to happen to your confrontational, but much smaller(?) cat.

Just to say that I agree with all of the above, also if the dog is bigger than the cat, keep the dog on a leash during early interactions with the kitten. Otherwise let the cat settle in somewhere away from the dog for at least a few days, and supervise any interaction at this point.

Good luck with the new kitty, and welcome to TCS