The overall survival rate for patients with head neck squamous cell carcinoma remains disappointingly static despite improved locoregional control. This has been attributed to the development of distant metastases and second primary malignancies in these patients, a large proportion of which occur in the thorax. We retrospectively analysed the incidence of thoracic malignancies in 138 patients presenting with newly diagnosed (n = 107) or recurrent (n = 31) cancer of the head and neck over a 4-year period. All 138 patients had undergone both computerised tomography of the thorax (CT) and conventional chest radiography within one month of presenting with biopsy proven squamous cell carcinoma. Seventeen percent of these were found to have simultaneous thoracic malignancies. CT thorax was more sensitive in detecting simultaneous thoracic malignancies compared with standard chest X-ray (24/138 versus 9/138, odds ratio of 3:1 in favour of CT). All thoracic malignancies detected by chest X-ray were also detected by CT thorax. Patients presenting with recurrent tumors were significantly more likely to have simultaneous thoracic malignancies than those with newly diagnosed cancer (11/31 versus 13/107, chi2 test with Yates correction, chi2 = 4.66, p = 0.03). The primary site (laryngeal, oral or pharyngeal) or presence of nodal disease did not have an effect on the incidence of simultaneous thoracic malignancies. The presence of distant metastases and second primary malignancies has major implications in the management and prognosis of patients presenting with head and neck squamous cell carcinoma, with a large proportion of such patients succumbing to their disease within one year of diagnosis. As CT scanning of the thorax was a more effective screening investigation than standard chest X-ray in the detection of simultaneous thoracic malignancy, we recommend it for use in the staging of patients presenting with cancer of the head and neck.