Objective: To determine if a hyaluronic acid/carboxymethylcellulose (HA/CMC) sinus dressing reduces the rate of postoperative scarring. Methods: In a randomized, matched-controlled, single-blinded study, following the completion of surgery, an HA/CMC dressing was randomly assigned to one side with the opposite unpacked side serving as a control. Results: Fifty-three patients underwent surgery for chronic rhinosinusitis (CRS; 39 patients) or CRS with nasal polyposis (14 patients). At the 8-week follow-up, there was no difference in synechiae on the HA/CMC side compared to the control (p = 0.09). HA/CMC-treated sinuses, however, demonstrated fewer synechiae in the first 2 weeks postoperatively compared to the control (p = 0.01), and were associated with significantly less nasal congestion at the 4-week (p = 0.02) and 8-week follow-up visits (0.03). Conclusion: There was no long-term difference in the rate of synechiae in the HA/CMC-treated sinus compared to the control. However, less severe nasal congestion and synechiae in the initial postoperative period may reduce the need for aggressive sinus debridement. Copyright © 2010 S. Karger AG, Basel.