If you mean placing ceramic tiles over existing vinyl tiles on the floor, yes you can... with a couple of caveats. Firstly, is the floor under the existing vinyl sound? That is, does it bounce, squeak or give when you walk across it? If any of the above exist you should deglaze the vinyl with a fine grit sandpaper, spread the same adhesive your going to use to lay the ceramic, but use a cement board screwed down (one screw every 8 inches) as an underlayment. There are several good products, but you should probably only need one that is 1/4 inch thick, rather than the heavier 1/2 inch one. This will eliminate cracking of the grout or worse cracking of the tiles themselves. If the floor is sound or if you're fortunate to have a cement floor under the vinyl, such as a basement, then, again, deglaze the vinyl, get rid of any wax and assure it's sufficiently roughned and then lay the tile as normally done... Best of luck...