Rapid palatal expansion may affect not only maxillary dimensions but also upper airway patency in adolescents; however, the role of tooth-supported and miniscrewassisted appliances remains to be clarified. This study aimed to assess morphological and functional changes in the upper respiratory tract associated with rapid palatal expansion and to compare these changes between the use of Hyrax and MARPE systems. We conducted a prospective pilot study involving 24 adolescents aged 12–16 years with transverse maxillary insufficiency. Fourteen participants received Hyrax appliances, while ten received MARPE devices. Time points: T0 — before treatment, T1 — 6 months after completion of activation. The measured indicators were the volume of the nasal cavity, nasopharynx, and oropharynx, the minimum area of the retropalatal level, and the total nasal resistance at 150 Pa. We also calculated the NOSE score. After treatment, the volume of the nasal cavity increased by 14.6% (p < 0.001), nasopharyngeal volume by 8.9% (p = 0.003), the minimum area of the retropalatal level by 12.1% (p = 0.012), total nasal resistance decreased by 24.7% (p < 0.001), and NOSE score by 35.4 points (p < 0.001). The change in oropharyngeal volume was insignificant (p = 0.091). We established no differences between Hyrax and MARPE groups (p > 0.05). Rapid palatal expansion improved nasal cavity and nasopharynx parameters. Further comparisons of techniques require a priori sample size calculations.