SQL 'Case When...'

Hi,

Don't know if it's possible, but how do I make the following SQL
statments right?

table
-------
name int4
attribute text[]

select attribute[1]
from table
case when attribute[1]='yes'
then select attribute[2] from table
else select attribute[3] from table;

Basically, I want to compare attr[1], if true then select some fields
from table; if false then select others.

Thank you.

- Bernie