The supraomohyoid neck dissection is a selective cervical node dissection that removes the contents of the submental and submandibular triangles (lymph node level I), the jugulodigastric and jugulo-omohyoid lymph node groups, and the lymph node-bearing tissues located anterior to the cutaneous branches of the cervical plexus and above the omohyoid muscle (lymph node levels II and III).
Source: wiktionary