Never tried it with CD's, but: If scratches in plastics are not too deep you have a good chance to polish them away. That means to make them invisible, and that should be what is needed in that case.

All you need is some polishing past (is that the word in english or what is correct?). Toothpast (the white-looking kind) is some very fine kind of this. I would try it first with a very soft, very clean cloth, it's unlikely to damage the CD. If this doesn't work I would get some coarser polishing past (not recommendable for teeth).

I would NOT try to somehow fill the scratches. For this I would need some material of exactly the same refractive index as the lacquer on the CD, and when applied, and provided it sticks I would first have to grind and still polish it to the extremely even surface shape of the CD before being able to test the result without the risk of damaging my player.

Joerg