Background: Transoral dioxide laser resection of early tumors (Tis, T1, T2) in the aerodigestive tract seems to be an established method of treatment. Recently, large tumors (T3 and T4) have been treated by this surgical method too, and therefore it seems reasonable to assess the complication rates., Material and Methods: All consecutive patients operated on primarily, with curative intention by means of carbon dioxide laser from February 1998 to February 2008 were prospectively registered in a SPSS-databank. Besides all data on the tumors and the surgery all types of complications were collected prospectively and updated weekly. Depending on their treatment, complications were divided into "minor" or "major". All patients with a minimum follow-up of 36 months were considered. The one-sample Kolmogorov-Smirnov test was used to study the distribution of the variables. Correlation between the variables was calculated with the Spearman test. The Mann-Whitney-U test was used to compare groups. All calculations were performed in a SPSS Windows 14.0 version;, the significant value for p was established at <. 05., Results: Six-hundred and eighty patients fulfilled the selection criteria. Postoperative bleeding and aspiration pneumonia were among the most frequent complications, the rate of "major" complications being 5.6%. Large tumors (T3, T4) and tumors of the supraglottis and the pyriform sinus had a statistically significant higher probability (p<0.001) to suffer a postoperative complication., Conclusions: After carbon dioxide laser surgery of malignant tumors of the upper aerodigestive tract postoperative complications may happen. Large tumors and those located in the supraglottis and the pyriform sinus have a statistically higher probability to develop a complication.