how to lookup a user, in LDAP thru jndi

Hi, I am trying to find an user cn= user1, in the LDAP thru jndi.

first I get the initialContext, then use the method lookup("cn=user1");

the tree structure is ou=ibm,c=us,ou=company,cn=user1.

but its always returning me nameNotFound.

can anyone help me with this one
thx in advance.