To evaluate the influence of the height of the antrostomy on dimensional variations of the elevated space after sinus floor elevation.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 (CBCT) scans were taken before surgery (T0) and after 1 week (T1) and 9 months (T2). Dimensional variation analyses were performed.The CBCT scans 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.In maxillary sinus floor elevations performed by the lateral approach, the size of the antrostomy did not affect the clinical and radiographic outcomes.