Obstructive sleep apnea (OSA) is a well-known risk factor for cardiovascular diseases. Several studies have shown that OSA is associated with vessel remodeling, but few studies have examined aorta. Aim: to analyse aortic remodelling in OSA. Methods: Thirty consecutive OSA patients (22 males and 8 females, aged 58.5 ± 13.2 years) were studied. All patients underwent a morning blood gas analysis, a full cardiorespiratory evaluation, including nocturnal polygraphy and echocardiography, that assessed aortic root diameter (ARD) and aortic stiffness index (ASI). Patients were grouped as follows: Group 1, non-severe OSA (Apnea-Hypopnea Index; AHI <30, 14 patients); Group 2, severe OSA (AHI ≥30, 16 patients). Results: No difference was found between the groups in ARD as absolute value (Group 1, 33.64 ± 0.91 mm; Group 2, 33.64 ± 1.02, p = ns) and as normalized value for the body surface area – ARDi (Group 1, 16.72 ± 0.63 mm/m2; Group 2, 16.09 ± 0.44, p = ns). Moreover, no difference was found in the ASI (Group 1, 14.04 ± 2.26; Group 2, 13.41 ± 2.22, p = ns). Considering all OSA patients, AHI showed an inverse correlation with ARDi (p = 0.018) and ASI (p = 0.0449). Moreover, the ASI showed a direct correlation with ARDi (p = 0.01) and morning PaO2 (p = 0.0349) as well as an inverse correlation with the oxygen desaturation index (ODI, p = 0.031) and total time with apnea and hypopnea (p = 0.039). Conclusion: No difference was found between severe and non-severe OSA in ARD. Surprisingly, the data show that the severity of OSA correlates inversely with the ASI and ARDi. The relation between PaO2 and stiffness might be explained by a feedback mechanism that tries to overcome the reduction of aortic elasticity due to night desaturation. These findings need to be investigated in further studies with a larger study population.