Objectives: In patients with chronically diseased maxillary sinuses, poor mucociliary clearance may result from long-standing inflammation or scarring from previous surgery. Endoscopic extended maxillary mega-antrostomy is a recently described technique that facilitates mucus clearance and sinus irrigation in terminally dysfunctional maxillary sinuses by allowing the sinus to drain by gravity alone. As the procedure is a modification of the medial maxillectomy and it is standard to perform dacryocystorhinostomy (DCR) at the end of a medial maxillectomy procedure, it was our intent to determine if a DCR is likewise indicated after mega-antrostomy. As a first step towards this answer, we aimed to study the relationship of the lacrimal system to the mega-antrostomy procedure using cadaveric dissection. Methods: In 12 operated sides, the nasolacrimal duct was violated 42% of the time during anterior dissection. The average anterior-posterior distance was 29.8mm. Lacrimal system violation occurred at an average of 3.7mm posterior to the anterior maxillary line. Unpaired Student t-test was performed to determine if the limit of anterior dissection was associated with lacrimal system penetration. Results: More anterior dissection was significantly associated with lacrimal system penetration (6.1mm negative penetration to 4.6mm positive penetration p=0.038) however the overall AP diameter was not significantly related to penetration (p=0.511). Conclusions: Our results indicate that lacrimal system injury is highly likely to occur during mega-antrostomy. To this end, DCR is indicated after mega-antrostomy. However, using the maxillary line as a surgical landmark, damage may be avoided by maintaining a distance of >7mm from the anterior most aspect of the dissection.