Context: Maxillary deficiency can lead to the reduction of airway space and increase the chances of development of obstructive airway disorders. Facemask therapy is one of the main treatment protocols in developing maxillary deficient patients. Objectives: The purpose of this systematic review and meta-analysis was to assess the changes in the airway dimensions after face-mask therapy in both cleft lip and palate and non-cleft patients. Data Sources: A systematic search in different electronic databases (EMBASE, Pubmed, Cochrance Central register of controlled trials), IADR proceedings and a hand search by October 2020 were conducted and a meta-analysis and systematic review was performed. Results: In patients without cleft lip and palate, upper pharyngeal width was significantly increased by mean of 2.05mm (CI = 95%, 0.61 - 3.50) following facemask therapy in comparison to patients who did not receive the treatment.Other upper pharyngeal (nasopharyngeal) measurements also showed a statistically significant improvement after therapy: S-PNS by 4.64mm (CI = 95%, 3.34 - 5.94), AD1-PNS by 3.81 mm (CI = 95%, 2.40 - 5.21), AD2-PNS by 2.90 mm (CI = 95%, 0.13 - 5.67) and Pm’-SPL by 2.53 (CI = 95%, 0.54 - 4.51). Lower pharyngeal measurments did not show any significant changes after the treatment (P > 0.05).In the analysis of studies with 3D imaging modalities, upper pharyngeal volume was also significantly increased by 499.29mm3 (CI = 95%, 69.58-929.00) after the treatment. In addition, a review of articles that included cleft lip and palate patients also showed after the treatment, the upper pharyngeal measurements all showed a significant improvement (P < 0.05), whereas the oropharyngeal region was relatively stable. Conclusions: In maxillary deficient patients with or without an orofacial cleft, facemask therapy can improve the nasopharyngeal area dimensions; however, this treatment protocol appears not to have an effect on the oropharyngeal area of the airway tract.