Yes you can lien leasehold interests. You may want to prepare the Lien so that it identifies the fee owner and the lessee as owners of their respective interests. Sometimes Fee Owners have clauses in their leases that prohibit liens of tenant contractors from attaching to the fee simple interest of the Landlord. Difficult to know at time of lien filing so good practice is to name both interests in the Lien and if you have to partially satisfy the Lien later by releasing the Lien against the Fee Owner only, you can do that without losing lien rights against the tenant with whom you contracted.