Background <p>Impaction of maxillary canines may narrow the maxillary sinus volumetrically that may be a predisposed factor in difficulty of maxillary sinus functions. This study aimed to investigate whether the presence of unilateral palatally impacted canine teeth resulted in differences in maxillary sinus volume and dimensions between the impacted and erupted sides.</p> Methods <p>Twenty-eight patients (female <i>n</i> = 23, male <i>n</i> = 5, and age range 13–36 years) were included in this study. Maxillary sinus volume, hemi-arch length, and hemi-arch width measurements were performed on the cone beam computed tomography (CBCT) records of the patients with a split-mouth design. The Mann–Whitney U test was used to compare the numerical measurements in the two groups, and the Wilcoxon signed-rank test was used to compare the measurements of impacted and nonimpacted sides.</p> Results <p>The values for maxillary sinus volume did not differ between the impacted and nonimpacted sides of the maxillary canine tooth (<i>p</i> = 0.265). The hemi-arch length was significantly shorter on the impacted side compared with the nonimpacted side (<i>p</i> &lt; 0.001). The transversal hemi-arch width measurement at 7&#xa0;mm on the impacted canine side was narrower than that on the nonimpacted side (<i>p</i> = 0.009).</p> Conclusions <p>The volumes of the sinus were similar on the impacted canine and erupted canine sides of the maxilla. The presence of a unilaterally impacted maxillary canine was associated with a decrease in the hemi-arch length and the anterior transversal width of the hemi-arch on the impacted side compared with the erupted side.</p>