Null chekcing is not workig properly in CF8

My variable and value is coming along with list of variables. I tried to check the variable conditions like
"<"cfif variablename) eq "" ">"
"<"cfset variablename = "New" ">"
"<"/cfif">"
But this condition not at all checking. Then i used below len() function.

Use below condition to check variable nulls in cf8
"<"cfif len(variablename) eq 0 ">"
"<"cfset variablename = "New" ">"
"<"/cfif">"