Query with conditional statement

Hi,

Can a conditional CASE statement be part of the SELECT portion of a query?
For example:

SELECT
fld1, fld2, fld3,
CASE
WHEN condition1 THEN fldx1 AS a1, fldx2 AS a2, fldx3 AS a3
WHEN condition2 THEN fldy1 AS b1, fldy2 AS b2, fldy3 AS b3
ELSE .....
END,
fld6, fld7
FROM ......
WHERE ......

I ran a test and see the following:
* Each WHEN only accepts 1 result and not 3 as shown in the example
* The AS for the alias is not supported

I need to return more than 1 field on each WHEN and also assign an ALIAS.
I very much appreciate your feedback.

Regards,
Jorge Maldonado