Background: Head and neck cancers are the seventh most common cancer worldwide, with squamous cell carcinoma accounting for 90% of cases. Accurate workup and staging is essential. Positron emission tomography/computed tomography (PET/CT) is widely accepted as a primary investigation when managing patients with suspected unknown primary, recurrent/advanced disease, melanoma, nasopharyngeal cancer and human papilloma virus (HPV) positive oropharyngeal cancer. The role of PET/CT in other head-neck mucosal malignancies is not clearly defined. The aim of this study is to evaluate the outcomes of PET/CT versus routine CT in this head and neck malignancy cohort. Methods: A single center retrospective cohort study, reviewing all patients discussed at our institution Head and Neck Multidisciplinary Meeting (MDM) between January 2020 and December 2021. Including those who underwent a PET-CT scan. The primary outcomes measured were second primary tumours (SPTs) detected or significant change to management. Results: A total of 279 patients were identified, with 92 patients included for analysis. 62 were male (67.4%). Median age 72 (IQR 62.5-80). 68 were NZ European (73.9%) and 11 were Maori (11.9%). 17 patients (18.5%) had SPT picked up on PET-CT that were not detected on CT. 23 (25.0%) had significant changes to management. 8 (34.8%) of these needed further surgical treatment with 4 (17.4%) deferred for palliative intent. 23 (25.0%) had additional lymphadenopathy seen on PET/CT. Within this 13 (56.5%) had changes to the TNM staging. 33 (35.9%) required further investigations. Conclusion: These findings support an expanded role of PET-CT in head and neck cancer which may improve staging and overall patient management.