While standard guidelines for Intensity Modulated radiation therapy (IMRT) may assist in target delineation for some head and neck (HN) cancers, the complex anatomy, varying patterns of spread, frequent occurrence of unusual or advanced presentations, and risk of treatment-related toxicities from overly generous delineation render HN treatment planning (TP) very challenging. Since 2007 we have had weekly Treatment Planning Quality Assurance (TPQA) rounds with radiation oncologists and a specialized diagnostic neuroradiologist present to review TP contours for all new patients. This study quantifies the impact of this process. From 8/2010 - 2/2011, IMRT contours for 84 consecutively treated HN cancer patients were reviewed. Almost always, pre-treatment magnetic resonance imaging (MRI) was reviewed independently and fused in multiple orientations to the computed tomography TP scan using a commercial software package; thus the contours could be viewed by the group directly opposed to the MRI if desired. Pre- and post-TPQA rounds contours were saved. For this study, the pre- and post-TPQA contours were compared to record alterations in the coverage of major components (gross tumor, clinical target volume (CTV), lymph nodes, perineural invasion, or bone invasion) and the volume of change. The tumors were mostly advanced stage (III-IV) and included various subsites: oral cavity (21%), oropharynx (19%), sinonasal (12%), skin (12%), nasopharynx (10%), salivary gland (8%), and hypopharynx (6%). Of the 84 cases, 47 (56%) were altered, including: CTV, 30/47 cases (64%); gross tumor, 25/47 cases (53%); lymph nodes, 7/47 (15%); perineural invasion, 6/47 (13%); and bone invasion, 3/47 (6%). The absolute volume change resulting from TPQA review ranged from -169.12 cc to 124.76 cc (0.03% to 636.88% of absolute pre-TPQA volume), with a mean absolute change of 32.32 cc (39.48%) and a median change of 13.54 cc (8.96%). Volumes were equally likely to be increased (49%) or decreased (51%). The most frequently altered subsites were: hypopharynx (4/5, 80%), sinonasal (7/10, 70%), and skin (7/10, 70%). This study demonstrates the impact of a neuroradiology-based approach to HN TPQA. Changes were suggested to half of the cases, and the changes were equally likely to increase or decrease the target volume, suggesting a balance between tumor coverage and desire to avoid toxicity. High frequencies of changes were seen in delineation of gross tumor and CTVs because of the wide applicability of these issues, but in addition, there are specific anatomic subsites with challenging patterns of infiltrative, intracranial, or perineural spread which warrant intensive imaging-based review in collaboration with a diagnostic specialist.