Within this work, we present a usability study on head motion and head gesture based human-robot interaction. The hands-free interface has been developed to support disabled people who cannot use their upper limbs. The presented pilot study was carried out with 24 able-bodied subjects at the age from 19 to 67 years. The subjects controlled an assistive robot with head motions and head gestures to perform several pick and place tasks. The evaluation has been carried out objectively as well as subjectively. The interaction design has been proven successful and assessed overall positive by the subjects.