Fifty-six patients with head and neck squamous cell cancer and N2 disease treated with chemoradiotherapy were evaluated for persistent or recurrent neck disease. Tumor characteristics analyzed were primary site, T category, nodal size (<3 cm or>or =3 cm), nodal necrosis based on hypodensity of one-third or more of the node, and type of N2 disease (N2a, N2b, or N2c). Forty-eight of the 56 patients underwent CT-PET to determine treatment response after chemoradiotherapy