hexdecimal constant in postgresql

hello,

i was wondering how to specify hexadecimal constants in
SQL in a way that postgresql understands.

something like:

select 0xFFFF;   -- this doesn't work;

I've googled for it and i've found it can be done with
encode/decode involving a bytea type - but i'm under
the impression there must be a more straightforward way...

Bye, Chris.