DON'T do it. While sometimes it will work, the majority of the time it will just hurt the disc (depending on the brand). Also, how deep are the scratches? Left us too many variables.
Yes, it does really work, but of course it depends on the depth of the scratches. If the disc is just dirty, just use a clean cotton t-shirt wiping from the inside out, not in a circular motion.
If the disc is scratched, you can try a basic white toothpaste, and rub it around lightly, after a minute or two, or when the toothpaste begins to dry, stop and wipe off using a clean cotton t-shirt, remember from the inside out.
In some cases, you can even run the disc under water to clean the toothpaste off, it will not hurt the disc unless it has a paper label on the disc. Most are lasered on the disc and will not be affected by the water.