Purpose: To evaluate the influence of the height of the antrostomy on dimensional variations of the elevated space after sinus floor elevation. Materials and Methods: Twenty-four healthy volunteers planned for sinus floor elevation were included in the study. An antrostomy of either 4 mm (group A) or 8 mm (group B) in height was prepared in the lateral wall of the sinus. Cone beam computed tomography scans (CBCTs) were taken before surgery (T0) and after 1 week (T1) and 9 months (T2). Dimensional variation analyses were performed. Results: The CBCTs of 10 patients per group were evaluated. After 1 week (T1), the sinus floor was found elevated in the middle region by 12.0 ± 2.3 mm in group A, while in group B, the height was 11.8 ± 2.1 mm. After 9 months (T2), the respective heights were 9.9 ± 2.4 mm and 8.9 ± 2.7 mm, with a reduction of -2.1 ± 2.2 mm in group A and -3.0 ± 2.6 mm in group B. The area in a central position was reduced by 25.5% to 34.2%, showing a slightly higher shrinkage in group B compared with group A. However, no statistically significant differences were found between the two groups. Conclusion: In maxillary sinus floor elevations performed by the lateral approach, the size of the antrostomy did not affect the clinical and radiographic outcomes. Keywords: antrostomy size, biomaterial, cone beam tomography, maxillary sinus, sinus augmentation, sinus dimension, sinus height