No, you can't tile to the plywood directly as wood is prone to warping.
Either backerboard or concrete board is fine, but I'd recommend backerboard
if it's for the wall, as it's lighter (it's also easier to cut).

BTW, is the plywood on the wall? Odd.
"Al Kondo" wrote in message
...
I am going to put 4" x 4" ceramic wall tile in my kitchen. Currently
there is 3/8" plywood underneath the current covering (I don't know
what you call it, but it is 1/4" glossy cover with fake 4" patterns so
that it looks like tile). I was thinking of removing the covering and
then possibly putting tile over the plywood. Alternatively, I could
put cement backerboard over the plywood. Should I go the backerboard
route, or, is it possible to tile over the plywood directly??

Thanks, Al Kondo