Apart from the function TRIM(), which removes leading, trailing and
multiple sequential spaces I cannot suggest anything more concrete as
"compare" is too vague. If you need to search a certain value in a
table, where this value might appear with additional spaces, you can do
the following:

=VLOOKUP(A1, TRIM(C2:C100), 2, 0)

This one needs to be array-entered (Shift+Ctrl+Enter).

On the other hand, if you are guaranteed the other table is free of
extra spaces but your current one might have some, you use the
opposite:

=VLOOKUP(TRIM(A1), C2:C100, 2, 0)

No need to array-enter this one.

Does this help?

Kostis Vezerides