Purpose: Marsupialization, designed to reduce the mandibular cyst volume, has continued to debated regarding its influence on the healing of the related bone cavity. The aim of the present study was to evaluate the 3-dimensional radiographic variation over time in mandibular odontogenic cystic lesions after marsupialization and assess the correlations between these variations and variables that can affect the procedure. Materials and Methods: We planned a retrospective cohort study. The predictor variables were the treatment duration, preoperative volume, patient age, histologic type, and number of preoperative residual bony walls. The outcomes variables were the postoperative volume reduction and the daily reduction rate calculated using computed tomography (CT) from before to after marsupialization using software designed for volumetric reconstruction and measurement of cyst-related bone defects. The descriptive and bivariate statistics were computerized, and the significance level was set at P = .05. Results: The sample included 15 patients (12 men and 3 women; mean age, 51.6; range, 27 to 85 years) affected by keratocysts (n = 6), dentigerous cysts (n = 6), and radicular cysts (n = 3) who had undergone marsupialization. The median duration of marsupialization was 406 days (25th to 75th percentile, 276 to 519). The mean AE standard deviation (SD) pre-and postdecompression volumes were 6,908.27 AE 2,669.058 and 2,468.13 AE 1,343.517 mm 3 , respectively (P < 0.001), and the mean AE SD percentage of reduction was 63.90 AE 13.12%. The volume decrease in the bone defects correlated positively with the treatment duration (P = .009) and preoperative volume (P < .001). However, no correlation was found with the other variables (P > .05) nor between the daily reduction rate and other variables (P > .05).