Please help: How to determine largest of two numbers in a query?

I have a table with the following structure:
yyyymmdd int4
key char(16)
value1 int4
value2 int4

with the following sample data:
yyyymmdd key value1 value2
19981201 hello 32 16
19981201 bye 29 64
19981202 hello 16 20
19981202 bye 23 13

What I need is to select the greatest between value1 and value2, so the
answer would be:
yyyymmdd key value
19981201 hello 32
19981201 bye 64
19981202 hello 20
19981202 bye 23

I can do this via ODBC using access by creating a column which is defined as
IF(value1>value2,value1,value2) but that doesn't work in psql.

How can I make this work in psql?

Thanks
Greg