Background: Overview of clinical impact of positron emission tomography-computed tomography (PET-CT) scans in patients with head and neck carcinomas at our center. Methods: Retrospective review of posttreatment 18F-fluorodeoxyglucose (18F-FDG) PET-CT scans in patients with head and neck carcinomas with risk of residual disease. Clinical outcome served as the reference standard. Results: This study included 93 patients (65.6% males, mean age: 48.8 years ± 17.2 standard deviation) with squamous cell carcinoma as most frequent histopathology (91.4%). PET-CT scans were performed on average 6 months posttreatment. Diagnostic accuracy, positive predictive value, and negative predictive value of PET-CT for disease were found to be 88%, 88%, and 92%, respectively. A median follow-up of 24 months was available for 91 patients. Kaplan–Meier curves showed significantly higher disease-free survival with negative PET-CT as compared to positive PET-CT (P = 0.01) and maximum standardized uptake values of <5.0 (P = 0.01). Conclusion: FDG PET-CT has diagnostic and prognostic implications in treated patient of head and neck cancers.