[dba-SQLServer] Does index field order matter?

I have three hash fields, person, family and address.  The hashes are a datatype VarBinary(200)  I 
then inner join one table to the next on the hash person.

I have a cover index on just those three fields.  So the question is, if I am primarily joining on 
let's say the person, does it help to have the person hash be the first column in the index?  Does 
the order of the fields in the index make any difference to performance getting at the data?

-- 
John W. Colby
www.ColbyConsulting.com