Objective: We compared positron emission tomography (PET) using 18-fluoro-2-deoxyglucose (FDG), enhanced computed tomography (CT) and magnetic resonance imaging (MRI) in detecting skull base invasion of nasopharyngeal carcinomas (NPC) and to evaluate the value of these three methods in determining the existence of skull base invasion of nasopharyngeal carcinomas. Methods: The images of enhanced CT, MRI and PET-CT scans, performed at intervals ≤ 20 days on 57 NPC patients from July 2004 to February 2007, were selected and reviewed. The endpoints of the comparison were sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of Enhanced CT, MRI and PET-CT, based on histopathologic findings or clinical imaging follow-up for at least 6 months. Results: For detecting skull base invasion of NPC, the sensitivity of enhanced CT, MRI and PET-CT were 68.18%, 84.09%, 97.67% respectively; specificity were 76.92%, 69.23%, 57.14% respectively; accuracy were 70.18%, 80.7%, 87.72% respectively; PPV were 90.9%, 90.24%, 87.5% respectively; NPV were 41.67%, 56.25%, 88.89% respectively. Conclusion: PET-CT has obvious advantages in sensitivity over CT (P < 0.05) and MRI, better than the two methods in accuracy and NPV and may be more valuable for new patients in detecting skull base invasion of NPC patients. Objective: We compared positron emission tomography (PET) using 18-fluoro-2-deoxyglucose (FDG), enhanced computed tomography (CT) and magnetic resonance imaging (MRI) in detecting skull base invasion of nasopharyngeal carcinomas (NPC) value of these three methods in determining the existence of skull base invasion of nasopharyngeal carcinomas. Methods: The images of enhanced CT, MRI and PET-CT scans, performed at intervals ≤ 20 days on 57 NPC patients from July 2004 to February 2007, were selected and reviewed. The endpoints of the comparison were sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of Enhanced CT, MRI and PET-CT, based on histopathologic findings or clinical imaging follow-up for at least 6 months. Results: For detection of skull base invasion of NPC, the sensitivity of enhanced CT, MRI and PET-CT were 68.18%, 84.09%, 97.67% respectively; specificity were 76.92%, 69.23%, 57.14% respectively; accurac PPV were 90.9%, 90.24%, 87.5% respectively; NPV were 41.67%, 56.25%, 88.89% respectively. Conclusion: PET-CT has obvious advantages in sensitivity over CT (P <0.05) and MRI, better than the two methods in accuracy and NPV and may be more valuable for new patients in detecting skull base invasion of NPC patients.