...or, if you have already run your select statement as part of your procedure, use this so you don't have to execute it a second time:
if @@ROWCOUNT > 0
SELECT 'Your TRUE block'
SELECT 'Your block for count(*) = 0'
@@ROWCOUNT stores the number of records returned by the last executed statement. If you don't use the value immediately, you will need to store it in a variable because it will change with your next statement.